JP2016012684A - Semiconductor light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element in which luminous efficiency of a semiconductor light emitting element is maximized by improvement in both of internal quantum efficiency IQE and light extraction efficiency LEE and further an upward output ratio is improved.SOLUTION: A semiconductor light emitting element (100) is formed by sequentially laminating at least an optical base material (10), a first semiconductor layer (30), a light-emitting semiconductor layer (40) and a second semiconductor layer (50) from below. The semiconductor light emitting element (100) includes a first fine concavo-convex structure (20) formed on a part of or on a whole area of a top face of the optical base material (10); and a second fine concavo-convex structure (60) formed on a top face of the light-emitting semiconductor layer (40) and/or a part of or a whole area of a surface located above the light-emitting semiconductor layer (40), in which a duty of the second fine concavo-convex structure (60) is smaller than a duty of the first fine concavo-convex structure (20).

Description

  The present invention relates to a semiconductor light emitting device.

  In recent years, various studies have been made to improve the light emission efficiency of light emitting diodes (LEDs). Such a semiconductor light emitting element has a configuration in which a high refractive index region including a light emitting portion is sandwiched between low refractive index regions. For this reason, the emitted light emitted from the light emitting portion of the semiconductor light emitting element becomes a waveguide mode that guides the inside of the high refractive index region, is confined inside the high refractive index region, is absorbed in the waveguide process, and is attenuated as heat. As described above, in the semiconductor light emitting device, the emitted light cannot be extracted outside the semiconductor light emitting device, and there is a problem that the light emission efficiency is greatly reduced.

  In the case of the LED element, as described below, the light extraction efficiency LEE (Light Extraction Efficiency) and the internal quantum efficiency IQE (Internal Quantum Efficiency), or the light extraction efficiency LEE and the electron injection efficiency EIE (Electron Injection Efficiency Efficiency E) By improving, a highly efficient LED element can be manufactured.

A GaN-based semiconductor element typified by a blue LED is manufactured by laminating an n layer, a light emitting layer, and a p layer on a single crystal substrate by epitaxial growth. As the single crystal substrate, a sapphire single crystal substrate or a SiC single crystal substrate is generally used. However, since there is a lattice mismatch between the sapphire crystal and the GaN-based semiconductor crystal, dislocations are generated inside the GaN-based semiconductor crystal (see, for example, Non-Patent Document 1). This dislocation density reaches 1 × 10 ⁹ pieces / cm ² . By this dislocation, the internal quantum efficiency IQE of the LED, that is, the light emission efficiency of the semiconductor is lowered, and as a result, the external quantum efficiency is lowered.

  The refractive index of the GaN-based semiconductor layer is larger than that of the sapphire substrate. For this reason, the light generated in the semiconductor light emitting layer is not emitted at an angle greater than the critical angle from the interface between the sapphire substrate and the GaN-based semiconductor layer. That is, a waveguide mode is formed, and heat is attenuated in the waveguide process. For this reason, the light extraction efficiency LEE decreases, and as a result, the external quantum efficiency EQE decreases. In addition, when a SiC substrate having a very large refractive index is used as the single crystal substrate, light emission at an angle greater than the critical angle from the interface between the SiC substrate and the air layer does not occur. In addition, a waveguide mode is generated, and the light extraction efficiency LEE decreases.

  That is, the internal quantum efficiency IQE decreases due to dislocation defects inside the semiconductor crystal, and the light extraction efficiency LEE decreases due to the formation of the waveguide mode, so that the external quantum efficiency of the LED greatly decreases.

  Therefore, a technique has been proposed in which a concavo-convex structure is provided on a single crystal substrate, and the light extraction efficiency LEE is increased by changing the light guiding direction in the semiconductor crystal layer (see, for example, Patent Document 1).

  In addition, a technique has been proposed in which the size of the concavo-convex structure provided on the single crystal substrate is nano-sized, and the pattern of the concavo-convex structure is randomly arranged (see, for example, Patent Document 2). Note that it has been reported that when the pattern size provided on the single crystal substrate is nano-sized, the light emission efficiency of the LED is improved as compared to a micro-sized pattern base material (for example, see Non-Patent Document 2).

  In addition, in order to further improve the light extraction efficiency LEE, a semiconductor layer is laminated on a growth substrate having a concavo-convex structure, particularly in face-up mounting, and the semiconductor layer corresponding to the light extraction surface on the upper surface is etched. A method of providing two layers of the concavo-convex structure is also disclosed (for example, see Patent Document 3).

JP 2003-318441 A JP 2007-294972 A JP 2013-168493 A

IEEE photo. Tech. Lett. , 20, 13, 1193 (2008) J. et al. Appl. Phys. , 103, 014314 (2008)

  In general, the factors that determine the external quantum efficiency EQE indicating the light emission efficiency of the LED include the electron injection efficiency EIE, the internal quantum efficiency IQE, and the light extraction efficiency LEE described above. Among these, the internal quantum efficiency IQE depends on (1) the dislocation density caused by the crystal mismatch of the GaN-based semiconductor crystal. The light extraction efficiency LEE is improved by (2) breaking the waveguide mode inside the GaN-based semiconductor crystal layer by light scattering or light diffraction by the concavo-convex structure provided on the single crystal substrate.

  However, in the conventional technology, the light emission efficiency of the semiconductor light emitting element is not maximized. In the technique described in Patent Document 1, the light extraction efficiency LEE is improved by the effect (2), but the effect of improving the internal quantum efficiency IQE by the effect (1) is small. This is because dislocation defects are reduced by the concavo-convex structure on the single crystal substrate. The concavo-convex structure disturbs the chemical vapor deposition (CVD) growth mode of the GaN-based semiconductor layer, and the dislocation defects accompanying the layer growth collide and disappear. It is to do. Therefore, setting the size of the concavo-convex structure to a nano-order pitch has a great effect on the reduction of the dislocation density, which is effective in improving the internal quantum efficiency IQE.

  In addition, when the size of the concavo-convex structure is nano-order, the wavelength is about several times the optical wavelength obtained by dividing the vacuum wavelength by the refractive index of the medium, and the wave nature of light is emphasized. The light extraction efficiency LEE is improved by breaking the waveguide mode by providing a nano-order uneven structure on the growth substrate, but the light has directivity in the region where the wave nature of light is emphasized. It is observed that there is still room for further improvement in the light extraction efficiency LEE by appropriately controlling the directivity.

  Also, in applications such as car headlights and projectors typified by projectors, which are typical applications of LEDs, the light distribution characteristics when used as a device largely depend on the light distribution characteristics of the light-emitting element light source. In the above application, it is advantageous that light is distributed upward of the chip.

  In Patent Document 3, a concavo-convex structure is provided on the growth base and the light extraction surface on the upper surface of the semiconductor layer in order to improve the light extraction efficiency LEE, but the concavo-convex structure on the upper surface of the semiconductor layer is formed by etching defects. And its placement is not controlled at all. That is, it was not a suitable concavo-convex structure for controlling the light distribution characteristics while keeping the efficiency of the LED high.

  The present invention has been made in view of the above problems, and provides a semiconductor light emitting device that improves both the internal quantum efficiency IQE and the light extraction efficiency LEE, and further improves the output ratio upward. Objective.

  As a result of intensive research in order to solve the above problems, the present inventor has a case in which the fine concavo-convex structure of the nanopattern provided on the optical substrate and the second fine concavo-convex structure provided thereon satisfy a specific condition It has been found that by improving both the internal quantum efficiency IQE and the light extraction efficiency LEE, the light emission efficiency of the semiconductor light emitting device is maximized and the output ratio to the upper side is further improved. That is, the present invention is as follows.

  The semiconductor light emitting device of the present invention is formed by laminating at least an optical base material, a first semiconductor layer, a light emitting semiconductor layer, and a second semiconductor layer in order from the bottom. A concavo-convex structure is formed, and a second fine concavo-convex structure is formed on the upper surface of the light-emitting semiconductor layer and / or a part of or the entire surface located above the light-emitting semiconductor layer. The duty of the concavo-convex structure is smaller than the duty of the first fine concavo-convex structure.

  With this configuration, since the duty of the second fine concavo-convex structure is smaller than the duty of the first fine concavo-convex structure, light distribution control in the upward direction of the semiconductor light emitting element can be performed while the light extraction efficiency LEE is high.

  In the semiconductor light emitting device of the present invention, it is preferable that a side surface inclination angle of the second fine concavo-convex structure is larger than a side surface inclination angle of the first fine concavo-convex structure.

  In the semiconductor light emitting device of the present invention, the ratio (Pav_2 / λ2) between the average pitch Pav_2 of the second fine concavo-convex structure and the second optical wavelength λ2 of the emitted light emitted from the light emitting semiconductor layer is 1.5 or more. It is preferable that the aspect ratio of the second fine concavo-convex structure is 0.2 or more and 1 or less.

  In the semiconductor light emitting device of the present invention, the second optical wavelength λ2 is preferably obtained by dividing the vacuum wavelength λ0 of the emitted light by the refractive index n2 of the layer having the second fine concavo-convex structure on the upper surface. .

  In the semiconductor light emitting device of the present invention, the ratio (Pav_1 / λ1) between the average pitch Pav_1 of the first fine concavo-convex structure and the first optical wavelength λ1 of the emitted light emitted from the light emitting semiconductor layer is 1.5 or more 5 The aspect ratio of the first fine concavo-convex structure is preferably 0.2 or more and 1 or less.

  In the semiconductor light emitting device of the present invention, the first optical wavelength λ1 is preferably the vacuum wavelength λ0 of the emitted light divided by the refractive index n1 of the first semiconductor layer.

  In the semiconductor light emitting device of the present invention, it is preferable that the first semiconductor layer, the light emitting semiconductor layer, and the second semiconductor layer are GaN-based semiconductors.

  According to the present invention, there is provided a semiconductor light emitting device in which both the internal quantum efficiency IQE and the light extraction efficiency LEE are improved so that the light emission efficiency of the semiconductor light emitting device is maximized and the output ratio is further improved. be able to.

1 is a schematic cross-sectional view showing a semiconductor light emitting element according to an embodiment. It is a cross-sectional schematic diagram which shows the other example of the semiconductor light-emitting device concerning this Embodiment. It is a cross-sectional schematic diagram which shows the other example of the semiconductor light-emitting device concerning this Embodiment. It is a cross-sectional schematic diagram which shows the other example of the semiconductor light-emitting device concerning this Embodiment. It is explanatory drawing for demonstrating the light distribution control of the side surface inclination | tilt angle of the 2nd fine concavo-convex structure which concerns on this Embodiment. It is explanatory drawing for demonstrating the effect of the side surface inclination | tilt angle of a 2nd fine concavo-convex structure. It is the top view which looked at the 1st semiconductor layer of the semiconductor light-emitting device concerning this Embodiment from the surface side in which the 1st fine concavo-convex structure was formed. It is the top view which looked at the 1st semiconductor layer of the semiconductor light-emitting device concerning this Embodiment from the surface side in which the 1st fine concavo-convex structure was formed. It is a top view which shows the case where the 1st fine uneven structure of the semiconductor light-emitting device concerning this Embodiment is a dot structure. It is a cross-sectional schematic diagram which shows the 1st fine concavo-convex structure in the line segment position corresponded to the pitch P shown in FIG. It is a top view which shows the case where the 1st fine uneven structure of the semiconductor light-emitting device concerning this Embodiment is a hole structure. It is a cross-sectional schematic diagram which shows the 1st fine concavo-convex structure in the line segment position corresponded to the pitch P shown in FIG. It is explanatory drawing for demonstrating the measuring method of the side surface inclination | tilt angle of the 1st fine concavo-convex structure which concerns on this Embodiment.

  Hereinafter, an embodiment of the present invention (hereinafter abbreviated as “embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

  First, the structure of the semiconductor light emitting device according to the present embodiment will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a semiconductor light emitting device according to the present embodiment. As shown in FIG. 1, in the semiconductor light emitting device 100, the optical substrate 10 has a first fine concavo-convex structure 20 formed on the upper surface thereof. A first semiconductor layer 30, a light emitting semiconductor layer 40, and a second semiconductor layer 50 are sequentially stacked from the bottom on the surface of the optical substrate 10 including the first fine concavo-convex structure 20. In FIG. 1, the first fine concavo-convex structure 20 can also be provided on a part of the upper surface of the optical substrate 10.

  Here, the emitted light generated in the light emitting semiconductor layer 40 is extracted from the upper second semiconductor layer 50 side or the lower optical substrate 10. Further, the first semiconductor layer 30 and the second semiconductor layer 50 are different semiconductor layers. Here, it is preferable that the first semiconductor layer 30 planarizes the first fine concavo-convex structure 20. By providing the first semiconductor layer 30 so as to planarize the first fine concavo-convex structure 20, the performance of the first semiconductor layer 30 as a semiconductor is reflected in the light emitting semiconductor layer 40 and the second semiconductor layer 50. Therefore, the internal quantum efficiency IQE is improved.

  The first semiconductor layer 30 may be composed of an undoped first semiconductor layer 31 and a doped first semiconductor layer 32, as shown in FIG. Here, the undoped first semiconductor layer 31 is provided so as to planarize the first fine concavo-convex structure 20, so that the performance of the undoped first semiconductor layer 31 as a semiconductor is the same as that of the doped first semiconductor layer 32, light emission. Since it can be reflected to the semiconductor layer 40 and the second semiconductor layer 50, the internal quantum efficiency IQE is improved.

  Furthermore, the undoped first semiconductor layer 31 preferably includes a buffer layer 33 as shown in FIG. In the semiconductor light emitting device 100, the buffer layer 33 is provided on the first fine concavo-convex structure 20, and then the undoped first semiconductor layer 31 and the doped first semiconductor layer 32 are sequentially stacked, whereby the first semiconductor layer 30. Since the nucleation and nucleation, which are the initial conditions for the crystal growth, are improved and the performance of the first semiconductor layer 30 as a semiconductor is improved, the degree of improvement in internal quantum efficiency IQE is improved. Here, the buffer layer 33 may be arranged so as to planarize the first fine concavo-convex structure 20, but since the growth rate of the buffer layer 33 is slow, the buffer layer 33 is buffered from the viewpoint of shortening the manufacturing time of the semiconductor light emitting device 100. It is preferable to planarize the first fine concavo-convex structure 20 with the undoped first semiconductor layer 31 provided on the layer 33. By providing the undoped first semiconductor layer 31 so as to planarize the first fine concavo-convex structure 20, the performance of the undoped first semiconductor layer 31 as a semiconductor can be improved by the doped first semiconductor layer 32 and the light emitting semiconductor layer 40. In addition, since it can be reflected in the second semiconductor layer 50, the internal quantum efficiency IQE is improved. In FIG. 1, the buffer layer 33 is disposed so as to cover the surface of the first fine concavo-convex structure 20, but may be partially provided on the surface of the first fine concavo-convex structure 20. In particular, the buffer layer 33 can be preferentially provided at the bottom of the concave portion of the first fine concavo-convex structure 20.

  Furthermore, on the upper surface of the second semiconductor layer 50 formed on the upper surface of the light emitting semiconductor layer 40, in other words, on the surface opposite to the surface facing the light emitting semiconductor layer 40 of the second semiconductor layer 50, the second fine layer is formed. An uneven structure 60 is formed. The second fine concavo-convex structure 60 is formed on the entire upper surface or a part of the upper surface of the second semiconductor layer 50. For example, in FIG. 1, the second fine concavo-convex structure 60 is also provided on the contact surface with the anode electrode 70, but the second fine concavo-convex structure 60 is the second semiconductor layer 50 excluding the contact surface with the electrode portion. It can also be provided on a part of the upper surface of the.

  Furthermore, the anode electrode 70 can be provided on the upper surface of the second semiconductor layer 50, and the cathode electrode 80 can be provided on the upper surface of the first semiconductor layer 30. The arrangement of the anode electrode 70 and the cathode electrode 80 is not limited because it can be optimized as appropriate by the semiconductor light emitting device, but is generally provided as illustrated in FIG.

  FIG. 2 is a schematic cross-sectional view showing another example of the semiconductor light emitting device according to the present embodiment. This is a case where a transparent conductive film 90 is provided on the second semiconductor layer 50. The transparent conductive film 90 can be provided on the second semiconductor layer 50, the anode electrode 70 can be provided on the transparent conductive film 90, and the cathode electrode 80 can be provided on the first semiconductor layer 30. The arrangement of the transparent conductive film 90, the anode electrode 70, and the cathode electrode 80 is not limited because it can be appropriately optimized by the semiconductor light emitting device, but is generally provided as illustrated in FIG. In FIG. 2, the transparent conductive film 90 covers the entire second fine concavo-convex structure 60, but may be provided so that a part of the second fine concavo-convex structure 60 is not covered.

  FIG. 3 is a schematic cross-sectional view showing another example of the semiconductor light emitting device according to the present embodiment. In FIG. 3, the second fine concavo-convex structure 60 is provided on the upper surface of the light emitting semiconductor layer 40. In addition, as shown in FIG. 3, the second fine concavo-convex structure 60 can be inherited to the upper surface of the second semiconductor layer 50 or the upper surface of the transparent conductive film 90. In FIG. 3, the second fine concavo-convex structure 60 may be provided on a part of the upper surface of the light emitting semiconductor layer 40. Moreover, although the 2nd fine concavo-convex structure 60 is covered with the 2nd semiconductor layer 50 and the transparent conductive film 90, one part may not be covered but may be exposed.

  FIG. 4 is a schematic cross-sectional view showing another example of the semiconductor light emitting device according to the present embodiment. In FIG. 4, the second fine concavo-convex structure 60 is provided on the upper surface of the transparent conductive film 90. In FIG. 4, the second fine concavo-convex structure 60 is formed on the entire or part of the upper surface of the transparent conductive film 90. The second fine concavo-convex structure 60 is also provided on the contact surface with the anode electrode 70, but the second fine concavo-convex structure 60 is a part of the upper surface of the transparent conductive film 90 excluding the contact surface with the electrode portion. You may make it the structure formed in.

  The semiconductor light emitting device 100 shown in FIGS. 1 to 4 is an example applied to a semiconductor light emitting device having a double hetero structure, but the stacked structure of the first semiconductor layer 30, the light emitting semiconductor layer 40, and the second semiconductor layer 50 is the same. It is not limited to.

  The semiconductor light emitting device 100 according to the present embodiment includes a first fine concavo-convex structure 20 formed on the entire upper surface or a part of the upper surface of the optical base material 10 and an upper surface of the light emitting semiconductor layer 40 or above the light emitting semiconductor layer 40. The second fine concavo-convex structure 60 formed on the entire surface or a part of the positioned surface is characterized in that the duty of the second fine concavo-convex structure 60 is smaller than the duty of the first fine concavo-convex structure 20.

  Since the duty of the second fine concavo-convex structure 60 is smaller than the duty of the first fine concavo-convex structure 20, light distribution control in the upward direction of the semiconductor light emitting element 100 can be performed while the light extraction efficiency LEE is high.

  In the semiconductor light emitting device 100 according to the present embodiment, the side surface inclination angle Θ of the second fine concavo-convex structure 60 is preferably larger than the side surface inclination angle Θ of the first fine concavo-convex structure 20.

  Since the side surface inclination angle Θ of the second fine concavo-convex structure 60 is larger than the side surface inclination angle Θ of the first fine concavo-convex structure 20, the light distribution control in the upward direction of the semiconductor light emitting device 100 is maintained while the light extraction efficiency LEE is high. Is possible. FIG. 5 is an explanatory diagram for explaining light distribution control of the side surface inclination angle of the second fine uneven structure according to the present embodiment. The arrows in FIG. 5 indicate the behavior of light. As shown in FIG. 5, when the side surface inclination angle Θ of the second fine concavo-convex structure 60 is larger than the side surface inclination angle Θ of the first fine concavo-convex structure 20, the semiconductor is formed by diffraction and scattering in the first fine concavo-convex structure 20. Light in the light emitting element 100 can be raised in the vertical direction. In addition, since the side surface inclination angle Θ of the second fine concavo-convex structure 60 is large, a component that forms an angle greater than a certain angle with the vertical direction among the light incident from the first fine concavo-convex structure 20 side is further angled by diffraction and scattering. It is possible to improve the luminance of the semiconductor light emitting device 100 in the upward direction.

  In the semiconductor light emitting device 100 according to the present embodiment, the ratio (Pav_1 / λ1) between the average pitch Pav_1 of the first fine concavo-convex structure 20 and the first optical wavelength λ1 of the emitted light emitted from the light emitting semiconductor layer 40 is 1. It is preferably 5 or more and 5 or less, and the aspect ratio of the first fine relief structure 20 is preferably 0.2 or more and 1 or less.

  The ratio (Pav_1 / λ1) between the average pitch Pav_1 of the first fine concavo-convex structure 20 provided on the surface of the optical substrate 10 and the first optical wavelength λ1 of the emitted light emitted from the light emitting semiconductor layer 40, and the first Since the aspect ratio of the fine concavo-convex structure 20 is in a predetermined range, the internal quantum efficiency IQE and the light extraction efficiency LEE can be improved.

  First, the internal quantum efficiency IQE can be improved. Specifically, by making the average pitch Pav_1 of the first fine concavo-convex structure 20 sufficiently small, it becomes possible to disturb the growth mode during film formation of the first semiconductor layer 30 on the optical substrate 10, and the first 1 Dislocations generated in the semiconductor layer 30 can be reduced.

  Further, since the ratio (Pav_1 / λ1) between the average pitch Pav_1 and the first optical wavelength λ1 of the emitted light is 1.5 or more and 5 or less, the wave nature of the light is emphasized, and the emitted light has directivity. Thereby, it becomes easier to control the emission direction by providing the second fine concavo-convex structure 60. Furthermore, when the aspect ratio is within a predetermined range, the volume change of the first fine concavo-convex structure 20 viewed from the light is sufficiently large, and the diffraction angle can advantageously break the waveguide mode, and the light extraction efficiency can be reduced. LEE improves.

  In the semiconductor light emitting device 100 according to the present embodiment, the ratio (Pav_2 / λ2) between the average pitch Pav_2 of the second fine uneven structure 60 and the second optical wavelength λ2 of the emitted light emitted from the light emitting semiconductor layer 40 is 1. 5 or more and 5.5 or less, and the aspect ratio of the second fine uneven structure 60 is preferably 0.2 or more and 1 or less.

  Since the ratio (Pav_2 / λ2) between the average pitch Pav_2 of the second fine uneven structure 60 and the second optical wavelength λ2 of the emitted light and the aspect ratio of the second fine uneven structure 60 are within a predetermined range, further light In addition to the improvement of the extraction efficiency LEE, the wave nature is emphasized, so that the light in the semiconductor light emitting device 100 having directivity in the first fine concavo-convex structure 20 can be further controlled upward. Furthermore, when the aspect ratio is within a predetermined range, the volume change of the second fine concavo-convex structure 60 viewed from the light is sufficiently large, and the diffraction angle can advantageously break the waveguide mode, and the light extraction efficiency can be reduced. LEE improves.

  In the semiconductor light emitting device 100 according to the present embodiment, the first optical wavelength λ1 of the emitted light can be obtained by dividing the vacuum wavelength λ0 of the emitted light by the refractive index n1 of the first semiconductor layer 30.

  Here, the emitted light refers to light emitted from the light emitting semiconductor layer 40 of the semiconductor light emitting device 100.

  As described above, when the first semiconductor layer 30 includes the buffer layer 33 and is formed by sequentially laminating the undoped first semiconductor layer 31 and the doped first semiconductor layer 32, the first optical of the emitted light. The wavelength λ1 is a wavelength in the undoped first semiconductor layer 31, that is, the first semiconductor layer 30 provided so as to flatten the first fine concavo-convex structure 20. As described above, the first optical wavelength λ1 of the emitted light is determined depending on the layer serving as the medium of the emitted light provided on the first fine uneven structure 20. This layer is called an “optical medium layer”. Here, the first semiconductor layer 30 is a first optical medium layer. Accordingly, the first optical wavelength λ1 of the emitted light can be calculated from the vacuum wavelength λ0 and the refractive index n1 of the first optical medium layer (first semiconductor layer 30).

  The vacuum wavelength λ0 of the emitted light is the vacuum wavelength of the light emitted by the light emitting semiconductor layer 40 in accordance with the band gap, and can be obtained by, for example, a wavelength meter or a spectral radiance meter.

  In the semiconductor light emitting device 100 according to the present embodiment, the second optical wavelength λ2 of the emitted light is obtained by dividing the vacuum wavelength λ0 of the emitted light by the refractive index n2 of the layer having the second fine concavo-convex structure 60 on the upper surface. can do. The layer having the second fine uneven structure 60 on the upper surface is defined as the second optical medium layer having the second fine uneven structure 60.

  The second optical medium layer is, for example, the second semiconductor layer 50 in the configuration as shown in FIG. 1 or FIG. 2, and the light emitting semiconductor layer 40 in the configuration as shown in FIG. 3, as shown in FIG. If it is a structure, it is the transparent conductive film 90.

  In general, the first semiconductor layer 30, the light emitting semiconductor layer 40, and the second semiconductor layer 50 are made of the same kind of elements and have different doping nuclides and concentrations. The impact on the department is small. Further, the light emitting semiconductor layer 40 or the second semiconductor layer 50 is generally much thinner than the first semiconductor layer 30, and it is substantially difficult to measure an accurate value. Therefore, when the second fine concavo-convex structure 60 is provided in the light emitting semiconductor layer 40 or the second semiconductor layer 50, the real part of the refractive index of the first semiconductor layer 30 is defined as the real part of the refractive index of the optical medium layer. It can also be equal.

  Hereinafter, the principle that the semiconductor light emitting device 100 according to the present embodiment exerts an effect will be described.

  In general, the light emission efficiency of a semiconductor light emitting device is determined by the internal quantum efficiency IQE and the light extraction efficiency LEE. In order to improve both, it is necessary to achieve both reduction of crystal defects due to the nano-order uneven structure and destruction of the waveguide mode. In particular, in order to break the waveguide mode, conventionally, a micro-order concavo-convex structure was provided on the growth substrate to scatter light and improve the light extraction efficiency LEE. We focused on the resulting light diffraction, especially the number of diffraction modes and the diffraction angle. As a result, the first fine concavo-convex structure 20 provided on the growth substrate 10 reduces the crystal defects when forming the semiconductor layer, and effectively breaks the waveguide mode by diffraction by the two fine concavo-convex structures. In addition to improving the internal quantum efficiency IQE and improving the light extraction efficiency LEE, the upward light distribution is strengthened from the magnitude relationship of the parameters that characterize the two fine concavo-convex structures. Became possible.

  First, the influence of the duty in the first fine concavo-convex structure 20 will be described. From the definition described later, a small duty means that if the flat portion of the first fine concavo-convex structure 20, for example, if the first fine concavo-convex structure 20 is an arrangement of a dot structure described later, there are many flat surfaces at the bottom of the concave portion. Yes. This is advantageous in terms of crystal growth because nucleation is likely to occur, but it is preferable that the number of flat portions that do not contribute to diffraction is small in terms of light extraction. In addition, since the second fine concavo-convex structure 60 is above the first fine concavo-convex structure 20, in order to increase light extraction from above the semiconductor light emitting device 100, the diffraction efficiency is increased and the waveguide mode is broken. It is necessary to move upward as much as possible. That is, it is preferable that the duty of the first fine concavo-convex structure 20 is large as long as crystal growth is not hindered.

  Next, the influence of the duty in the second fine uneven structure 60 will be described. The emitted light generated in the light emitting semiconductor layer 40 is extracted from the second semiconductor layer 50 side above the semiconductor light emitting element 100 or the optical substrate 10. Here, the presence of the second fine concavo-convex structure 60 makes it possible to increase the light component extracted from above the semiconductor light emitting element 100 and to control the light distribution characteristics. Here, in the second fine concavo-convex structure 60, the light path is only in one direction from the light emitting semiconductor layer 40 to the outside of the semiconductor light emitting element 100, and there are components extracted from the flat surface of the second fine concavo-convex structure 60. Further, when the duty is close to 1, it means that there are few flat portions and the distance between the convex portions is small, and light incident on the convex portions having the second fine concavo-convex structure 60 easily enters the adjacent convex portions. In addition, since the component returning to the inside of the chip increases, the degree of improvement in the light extraction efficiency LEE is reduced. That is, from the viewpoint of increasing the components that can be extracted from above the semiconductor light emitting device 100, it is preferable to have a flat portion at a certain ratio.

  Furthermore, since the duty of the second fine concavo-convex structure 60 is smaller than the duty of the first fine concavo-convex structure 20, it is possible to further improve the light extraction efficiency LEE and improve the upward luminance of the semiconductor light emitting device 100. This is due to the following reason.

  In order to further improve the light extraction efficiency LEE, when considering the path of the emitted light, the light emitted from the light emitting semiconductor layer 40 is directly extracted outside the device through the second fine concavo-convex structure 60, or It is preferable that it is a path that goes to the lower part of the element and enters an angle range that is easily transmitted through the second fine concavo-convex structure by diffraction and scattering at the first fine concavo-convex structure 20. Here, since the duty of the second fine concavo-convex structure 60 is smaller than the duty of the first fine concavo-convex structure 20, the vertical component is increased by the high diffraction efficiency in the first fine concavo-convex structure 20, and the second fine concavo-convex structure Since the flat surface of the structure 60 has a certain area ratio, it is possible to improve the upward luminance of the semiconductor light emitting device 100. Further, from the point of light extraction, the duty difference is preferably 0.05 or more, more preferably 0.1 or more. On the other hand, in order to prevent the ratio of the flat surface of the second fine concavo-convex structure from becoming too wide and difficult to contribute to light extraction, the duty difference is preferably 0.4 or less, and more preferably 0.35 or less.

  Next, the magnitude relationship between the side surface inclination angles Θ of the two fine concavo-convex structures will be described.

  First, the effect of the side surface inclination angle Θ of the second fine concavo-convex structure 60 will be described. In order to distribute light upward in the semiconductor light emitting device 100, it is necessary that light having a large angle with the vertical direction is diffracted and scattered in the vertical direction. FIG. 6 is an explanatory diagram for explaining the effect of the side surface inclination angle of the second fine concavo-convex structure. The arrows in FIG. 6 indicate the behavior of light incident on the second fine concavo-convex structure 60. In addition, although the locus of light is illustrated by an arrow, this does not mean that the second fine concavo-convex structure 60 can be described by geometrical optics, and merely illustrates a direction perpendicular to the wavefront of light. .

  As shown in FIG. 6A, when the side surface inclination angle Θ of the second fine concavo-convex structure 60 is small, light having a large angle with the vertical direction is not effectively diffracted and scattered in the vertical direction. On the other hand, as shown in FIG. 6B, when the side surface inclination angle Θ of the second fine concavo-convex structure 60 is large, light having a large angle with the vertical direction is effectively diffracted and scattered in the vertical direction. In particular, since the lower layer (second optical medium layer) having the second fine concavo-convex structure 60 on the upper surface is generally used as a thin film, it is difficult to form a shape with a high aspect ratio as shown in FIG. 6B. Therefore, the frustum as shown in FIG. 6C that can increase the side surface inclination angle Θ, or the columnar shape shown in FIG. 6D is preferable.

  Next, the magnitude relationship between the side surface inclination angles Θ of the two fine concavo-convex structures will be described. In the present embodiment, the side surface inclination angle Θ of the second fine concavo-convex structure 60 is preferably larger than the side surface inclination angle Θ of the first fine concavo-convex structure 20. This is presumed to be the following reason.

  Considering the light extraction path, since the second fine concavo-convex structure 60 is located above the first fine concavo-convex structure 20, in order to increase the light extraction from above the semiconductor light emitting device 100, the first fine concavo-convex structure 20 Therefore, it is necessary to increase the diffraction efficiency of the optical waveguide so that as many broken waveguide modes as possible are directed upward. As shown in FIG. 5, the side surface inclination angle Θ of the second fine concavo-convex structure 60 is larger than the side surface inclination angle Θ of the first fine concavo-convex structure 20, so that The light in the semiconductor light emitting device 100 is raised in the vertical direction by scattering, and the side surface tilt angle Θ of the second fine concavo-convex structure 60 is large. It is presumed that the upward luminance can be improved by further changing the angle of a component having a certain angle or more by diffraction and scattering. In FIG. 5, the lower layer (second optical medium layer) having the second fine uneven structure 60 on the upper surface is the second semiconductor layer 50, that is, the second fine uneven structure 60 is provided on the upper surface of the second semiconductor layer 50. However, as shown in other drawings, the second fine concavo-convex structure 60 is formed on the upper surface of the light emitting semiconductor layer 40 and / or at least a part or the entire surface located above the light emitting semiconductor layer 40. As long as the second fine concavo-convex structure 60 is formed. That is, since the side surface inclination angle Θ of the second fine concavo-convex structure 60 is larger than the side surface inclination angle Θ of the first fine concavo-convex structure 20, the light distribution control in the upward direction can be performed while the light extraction efficiency LEE is high. Become.

  In the semiconductor light emitting device 100 according to the present embodiment, the ratio (Pav_1 / λ1) between the average pitch Pav_1 of the first fine concavo-convex structure 20 and the first optical wavelength λ1 of the emitted light emitted from the light emitting semiconductor layer 40 is 1. It is preferably 5 or more and 5 or less, and the aspect ratio of the first fine relief structure 20 is preferably 0.2 or more and 1 or less.

  Next, the reason why the first fine concavo-convex structure 20 preferably satisfies the above conditions will be described.

  As described above, when the average pitch Pav_1 of the first fine concavo-convex structure 20 is sufficiently small, it becomes possible to disturb the growth mode during the film formation of the first semiconductor layer 30 on the optical substrate 10, and the first 1 Dislocations generated in the semiconductor layer 30 can be reduced, and the internal quantum efficiency IQE can be improved.

  Next, the reason why the above conditions are preferable in disturbing the waveguide mode in the first fine concavo-convex structure 20 will be described.

  In general, the interaction between the emitted light generated in the light emitting layer of the semiconductor light emitting element and the uneven structure is determined by the relationship between the optical wavelength λ of the emitted light in the semiconductor light emitting element and the size of the fine uneven structure.

  The micro-order concavo-convex structure conventionally used is about 10 times as large as the optical wavelength λ of the emitted light in the semiconductor light emitting device, and the interaction between the light and the concavo-convex structure is scattering. However, when the size of the concavo-convex structure is nano-ordered to improve the internal quantum efficiency IQE, the optical wavelength λ of the emitted light in the semiconductor light emitting device is about the same as the optical wavelength λ, and is about several times larger. It is emphasized that light diffraction occurs as an interaction.

  Factors that characterize optical diffraction are the mode, which is the number of intensifying directions after diffraction, the light output angle of each mode, and the intensity of each mode. In light diffraction, due to its wave nature, a plurality of intensifying directions are generated by reflection and transmission at the concavo-convex structure.

  The number of modes of light diffraction is small when the ratio between the average pitch and the optical wavelength is small, and increases as the ratio between the average pitch and the optical wavelength is large. That is, the number of modes is limited under the condition that the ratio between the average pitch and the optical wavelength is small. This is observed when the diffracted light has directivity.

  On the other hand, the number of modes of light diffraction increases as the ratio between the average pitch and the optical wavelength increases. At this time, the strength of each mode decreases as the number of modes increases. In addition, the distribution of the light emission angle gradually becomes wider. Its behavior is observed as scattered.

  In order to favorably break the waveguide mode by the first fine concavo-convex structure 20 and the second fine concavo-convex structure 60 and contribute to light extraction, the light inside the semiconductor light emitting element 100 preferably has directivity. . However, if the ratio between the average pitch and the optical wavelength is too small, the number of modes generated by diffraction and the light output angle of the modes are extremely limited, and it is difficult to effectively improve the light extraction efficiency. This is because light that passes through the first fine concavo-convex structure 20 includes a component that is incident on the optical base material from the semiconductor layer, and a component that is reflected on the bottom and side surfaces of the optical base material and is incident on the semiconductor layer again. In order to be mixed, the concavo-convex structure needs to be suitable in both directions. For this reason, if the number of modes and the light output angle of the modes are limited, it is difficult to achieve a structure that can truly maximize light extraction. Therefore, since the mode contributes to the light extraction under the directivity condition, the ratio between the average pitch Pav_1 of the first fine concavo-convex structure 20 and the first optical wavelength λ1 is preferably 1.5 or more. .6 or more is more preferable. The upper limit is preferably 5 or less.

  In the semiconductor light emitting device 100 according to the present embodiment, the ratio (Pav_2 / λ2) between the average pitch Pav_2 of the second fine uneven structure 60 and the second optical wavelength λ2 of the emitted light emitted from the light emitting semiconductor layer 40 is 1. 5 or more and 5.5 or less, and the aspect ratio of the second fine uneven structure 60 is preferably 0.2 or more and 1 or less.

  Similarly, the ratio between the average pitch Pav_2 of the second fine concavo-convex structure 60 and the second optical wavelength λ2 is preferably in the above range. In order to favorably break the waveguide mode by the first fine concavo-convex structure 20 and the second fine concavo-convex structure 60 and contribute to light extraction, the light inside the semiconductor light emitting element 100 preferably has directivity. . In the second fine concavo-convex structure 60, the light is only in one direction from the inside of the semiconductor light emitting device 100 to the outside, and the interface where the second fine concavo-convex structure 60 is provided corresponds to the light exit surface, so the number of modes is limited. However, the upward luminance is improved by setting the shape, height, and side surface inclination angle Θ to improve the intensity of the light component diffracted upward in the semiconductor light emitting element 100 out of the outward light. be able to. From the viewpoint of the number of modes, the ratio (Pav_2 / λ2) between the average pitch Pav_2 of the second fine uneven structure 60 and the second optical wavelength λ2 of the emitted light emitted from the light emitting semiconductor layer 40 is preferably 1.5 or more, Two or more are more preferable. Since the scattering is observed when the number of modes is too large, the ratio (Pav_2 / λ2) is preferably 5.5 or less.

  The first fine concavo-convex structure 20 and the second fine concavo-convex structure 60 provided in the present embodiment are composed of a plurality of convex portions or concave portions. If the fine concavo-convex structure has convex portions or concave portions, the shape and arrangement thereof are not limited, and the internal quantum efficiency IQE and the light extraction efficiency LEE can be increased. For this reason, for example, a line-and-space structure in which a plurality of fence-like bodies are arranged, a dot structure in which a plurality of dot (convex portions, protrusions) -like structures are arranged, a hole structure in which a plurality of hole (concave) -like structures are arranged, etc. Can be adopted. Examples of the dot structure and the hole structure include a cone, a cylinder, a quadrangular pyramid, a quadrangular prism, a hexagonal pyramid, a hexagonal pyramid, a polygonal pyramid, a double ring shape, and a multiple ring shape. These shapes include a shape in which the outer diameter of the bottom surface is distorted and a shape in which the side surface is curved. The dot structure is a structure in which a plurality of convex portions are arranged independently of each other. That is, each convex part is separated by a continuous concave part. In addition, each convex part may be smoothly connected by the continuous recessed part. On the other hand, the hole structure is a structure in which a plurality of recesses are arranged independently of each other. That is, each recessed part is separated by the continuous convex part. In addition, each recessed part may be smoothly connected by the continuous convex part.

  As the arrangement of the first fine concavo-convex structure 20 and the second fine concavo-convex structure 60, a regular hexagonal arrangement, a regular tetragonal arrangement, a quasi-hexagonal arrangement, a quasi-tetragonal arrangement, and the like can be adopted. Furthermore, a combination of these sequences can also be employed. For example, an array in which a regular hexagonal array and a regular tetragonal array are alternately arranged, an array that gradually changes from a regular hexagonal array to a regular tetragonal array, and gradually returns from the regular tetragonal array to the regular hexagonal array, and the like. Here, the quasi-hexagonal array is defined as an array in which the distance (pitch) between adjacent convex portions of the regular hexagonal array has a deviation of ± 15% or less. This deviation amount may be a uniform deviation amount in the array, or a distribution may be provided for the deviation amount. Moreover, the arrangement of the first fine uneven structure 20 and the second fine uneven structure 60 may be different from each other.

  Next, parameters used in the first fine uneven structure 20 and the second fine uneven structure 60 are defined. The first fine concavo-convex structure 20 will be described below, but the second fine concavo-convex structure 60 is similarly defined unless otherwise specified. The parameter measurement method will be described after the description of the parameters.

  Further, in the following description, the case where the first fine concavo-convex structure 20 has a dot structure will be described. However, in the description of the case of a hole structure, the following terms will be used in the same manner, except that they will be specifically distinguished. be able to.

<Pitch P and average pitch Pav_1>
FIG. 7 is a top view of the first semiconductor layer of the semiconductor light emitting device according to the present embodiment as viewed from the surface side on which the first fine concavo-convex structure is formed. When the first fine concavo-convex structure 20 is a dot structure in which a plurality of convex portions 20a are arranged in the concave portions 20b, the center of a certain convex portion A1 and the convex portions B1-1 to convex portions adjacent to the convex portion A1. A distance PA1B1-1 to a distance PA1B1-6 between the center of B1-6 is defined as a pitch P. However, as shown in FIG. 7, when the pitch P varies depending on the adjacent convex portions, the average pitch Pav_1 is determined according to the following procedure. (1) A plurality of arbitrary convex portions A1, A2,... AN are selected. (2) The pitches PAMBM-1 to PAMBM-k between the convex portions AM (1 ≦ M ≦ N) and the convex portions (BM-1 to BM-k) adjacent to the convex portions AM are measured. (3) For the convex portions A1 to AN, the pitch P is measured as in (2). (4) An arithmetic average value of the pitches PA1B1-1 to PANBN-k is defined as an average pitch Pav_1. However, N is 5 or more and 10 or less, and k is 4 or more and 6 or less. In the case of the hole structure, the average pitch Pav_1 can be defined by replacing the convex portion 20a described in the dot structure with a concave opening. The second fine concavo-convex structure 60 is defined similarly.

  FIG. 8 is a top view of the first semiconductor layer of the semiconductor light emitting device according to the present embodiment as viewed from the surface side where the first fine concavo-convex structure is formed. As shown in FIG. 8, when the first fine concavo-convex structure 20 is a line-and-space structure, the center line of a certain convex line A1, and the centers of the convex line B1-1 and the convex line B1-2 adjacent to the convex line A1. The arithmetic mean of the shortest distance PA1B1-1 and the shortest distance PA1B1-2 between the lines is defined as the pitch P. However, as shown in FIG. 8, when the pitch P differs depending on the selected convex line, the average pitch Pav_1 is determined according to the following procedure. (1) An arbitrary plurality of convex lines A1, A2,... AN are selected. (2) The pitches PAMBM-1 and PAMBM-2 between the convex lines AM (1 ≦ M ≦ N) and the convex lines (BM-1, BM-2) adjacent to the convex line AM are measured. (3) For the convex lines A1 to AN, the pitch P is measured as in (2). (4) An arithmetic average value of the pitches PA1B1-1 to PANBN-2 is defined as an average pitch Pav_1. However, N is 5 or more and 10 or less. The second fine concavo-convex structure 60 is defined similarly.

<Convex top width lcvt, concave opening width lcct, convex bottom width lcvb, concave bottom width lccb>
FIG. 9 is a top view showing a case where the first fine concavo-convex structure of the semiconductor light emitting element according to the present embodiment has a dot structure. FIG. 9 shows a top view when the first fine relief structure 20 has a dot structure. A line segment indicated by a broken line in FIG. 9 is a distance between the center of a certain convex portion 20a and the center of the convex portion 20a closest to the convex portion 20a, and means the pitch P described above. The second fine concavo-convex structure 60 is defined similarly. FIGS. 10A and 10B show schematic cross-sectional views of the first fine concavo-convex structure 20 at the line segment position corresponding to the pitch P shown in FIG. FIG. 10 is a schematic cross-sectional view showing the first fine concavo-convex structure at the line segment position corresponding to the pitch P shown in FIG.

  As shown in FIG. 10A, the convex portion top width lcvt is defined as the width of the top surface of the convex portion 20a, and the concave portion opening width lcct is a difference value (P−lcvt) between the pitch P and the convex portion top width lcvt. Defined. The second fine concavo-convex structure 60 is defined similarly.

  As shown in FIG. 10B, the convex bottom width lcvb is defined as the width of the convex portion 20a, and the concave bottom width lccb is defined as a difference value (P-lcvb) between the pitch P and the convex bottom width lcvb. Is done. The second fine concavo-convex structure 60 is defined similarly.

  FIG. 11 is a top view showing a case where the first fine concavo-convex structure of the semiconductor light emitting element according to the present embodiment has a hole structure. FIG. 11 shows a top view when the first fine relief structure 20 has a hole structure. A line segment indicated by a broken line in FIG. 11 is a distance between the center of a certain recess 20b and the center of the recess 20b closest to the recess 20b, and means the pitch P described above. The second fine concavo-convex structure 60 is defined similarly. 12A and 12B show schematic cross-sectional views of the first fine concavo-convex structure 20 at the line segment position corresponding to the pitch P shown in FIG. 12 is a schematic cross-sectional view showing the first fine concavo-convex structure at the line segment position corresponding to the pitch P shown in FIG.

  As shown in FIG. 12A, the recess opening width lcct is defined as the opening width of the recess 20b, and the protrusion top width lcvt is defined as a difference value (P−lcct) between the pitch P and the recess opening width lcct. The second fine concavo-convex structure 60 is defined similarly.

  As shown in FIG. 12B, the convex bottom width lcvb is defined as the width of the convex portion 20a, and the concave bottom width lccb is defined as a difference value (P-lcvb) between the pitch P and the convex bottom width lcvb. Is done. The second fine concavo-convex structure 60 is defined similarly.

<Duty>
In the case of the dot structure, the duty is defined by a ratio (lcvb / P) between the convex bottom width lcvb and the pitch P. On the other hand, in the case of the hole structure, it is defined by the ratio of the recess bottom width lccb to the pitch P (lccb / P).

  First, the influence of the duty in the first fine concavo-convex structure 20 will be described. From the above definition, a small duty indicates that there are many flat surfaces at the bottom of the recesses in the case of a flat part of the concavo-convex structure, that is, an arrangement of dot structures. This is advantageous in terms of crystal growth because nucleation is likely to occur, but it is preferable that the number of flat portions that do not contribute to diffraction is small in terms of light extraction.

  On the other hand, the upper limit of the duty is determined from the crystal growth of the semiconductor layer. If the area of the flat portion of the optical substrate is too small, nucleation during crystal growth is hindered, resulting in a decrease in crystal quality.

  Further, the diffraction is characterized by the volume of the convex portion 20a. In a dot structure or a hole structure, which is an array of independent protrusions 20a or recesses 20b, the duty is square with respect to the volume of the protrusions 20a. Considering the above, in the first fine concavo-convex structure 20, the duty is preferably 0.3 or more, and more preferably 0.5 or more, with respect to the arrangement of the convex portions 20a of the dot structure. The upper limit is preferably 0.91 or less, and more preferably 0.86 or less.

  Further, in the first fine concavo-convex structure 20 having continuous convex portions such as a line and space structure, the volume of the convex portions is linear with respect to the duty. Therefore, the duty is more preferably 0.3 or more, and most preferably 0.5 or more. The upper limit is preferably 0.83 or less, and more preferably 0.74 or less.

  Next, the influence of the duty on the second fine uneven structure 60 will be described. As already described, the emitted light generated in the light emitting semiconductor layer 40 is extracted from the second semiconductor layer 50 side above the semiconductor light emitting element 100 or the optical substrate 10. Here, the presence of the second fine concavo-convex structure 60 makes it possible to increase the light component extracted from above the semiconductor light emitting element 100 and to control the alignment characteristics. Here, in the second fine concavo-convex structure 60, the light path is only in one direction from the light emitting semiconductor layer 40 to the outside of the semiconductor light emitting element 100, and there are components extracted from the flat surface of the second fine concavo-convex structure 60. That is, from the viewpoint of increasing the components that can be extracted from above the semiconductor light emitting device 100, it is preferable to have a flat portion at a certain ratio.

  In a dot structure or a hole structure that is an array of independent convex portions or concave portions, the duty is squared with respect to the volume of the convex portions or concave portions. Considering the above, in the second fine concavo-convex structure 60, the duty is preferably 0.3 or more, and more preferably 0.5 or more, with respect to the arrangement of the convex portions 20a of the dot structure. The upper limit is preferably 0.8 or less, and more preferably 0.7 or less.

  Furthermore, in the second fine concavo-convex structure 60 having continuous convex portions such as a line and space structure, the volume of the convex portions is linear with respect to the duty. Therefore, the duty is more preferably 0.3 or more, and most preferably 0.5 or more. The upper limit is preferably 0.6 or less, and more preferably 0.5 or less.

<Height H>
The height H of the first fine concavo-convex structure 20 is defined as the shortest distance between the average position of the bottom of the concave portion 20b of the first fine concavo-convex structure 20 and the average position of the top of the convex portion 20a of the concavo-convex structure. The second fine concavo-convex structure 60 is defined similarly. The number of sample points for calculating the average position is preferably 10 or more.

  As the height H is larger, more modes and incident light interact from a group of diffraction modes determined by the average pitch Pav_1. In other words, when the height H is small, incident light acts only on the diffracted light of a limited mode from the group of diffraction modes determined by the average pitch Pav_1 through the first fine concavo-convex structure 20. When H is large, more diffraction modes in the group of diffraction modes determined by the average pitch Pav_1 interact with the incident light. That is, as the height H is larger, the interaction between the incident light and the first fine concavo-convex structure 20 becomes more scattering in behavior. The larger the height H, the more the modes interact, but this includes modes that do not contribute to light extraction. Therefore, if it is scattering, a loss occurs. Therefore, the first fine concavo-convex structure 20 does not need to have an excessively high shape.

  In particular, in the case where the fine concavo-convex structure is the first fine concavo-convex structure 20, the thickness of the first semiconductor layer 30 required for planarization can be reduced because the convex portion 20a is on the order of nanometers. Therefore, warpage and cracks in the semiconductor light emitting device 100 due to the difference in the lattice constant between the optical substrate 10 and the semiconductor layer or the difference in the thermal expansion coefficient can be suppressed. From the above viewpoint, the height H of the first fine concavo-convex structure 20 is preferably not more than 1 time of the average pitch Pav_1, and more preferably not more than 0.7 times.

<Aspect ratio>
In the case of a dot structure, the aspect ratio is a ratio of the convex portion height H and the convex portion bottom width lcvb, that is, (H / lcvb). On the other hand, in the case of the hole structure, the ratio between the recess depth H and the recess bottom width lccb, that is, (H / lccb).

  For the first fine concavo-convex structure 20 and the second fine concavo-convex structure 60, a large aspect ratio means that the height H is large, that is, many diffraction modes are established, and as a result, a mode contributing to light extraction is likely to be established. For this reason, the aspect ratio is preferably 0.2 or more, and more preferably 0.3 or more. In order to prevent the convex portions from being too high and being excessively diffracted and scattered, the aspect ratio is preferably 1 or less, more preferably 0.9 or less.

<Side angle Θ>
The inclination angle Θ of the side surface of the convex portion 20a is determined by the shape parameter of the first fine concavo-convex structure 20 described above. In particular, when the fine concavo-convex structure is the first fine concavo-convex structure 20, the inclination angle Θ on the side surface of the convex portion 20a may be selected from the crystal planes that appear on the side surface of the convex portion 20a, depending on the material of the growth substrate 10 and the semiconductor crystal layer. it can.

  In addition, the measuring method is shown in FIG. 13 about the convex part 20a side surface inclination | tilt angle (theta) at the time of comparing by a magnitude relationship. FIG. 13 is an explanatory diagram for explaining a method of measuring the side surface inclination angle of the first fine concavo-convex structure according to the present embodiment. The side surface inclination angle Θ of the convex portion 20a is not simply determined when the inclination angle changes in multiple steps, for example, when the convex portion 20a is hemispherical. Therefore, the convex portion 20a side surface inclination angle Θ used in this specification is “a portion corresponding to the bottom diameter (lcvb), around one third of the height H of the convex portion 20a, and three minutes of the height H. The total value is measured at a total of three points in the vicinity of 2 and the average value is taken as the measurement value for one convex portion.

  For example, in the case of the conical shape shown in FIG. 13A or the truncated cone of FIG. 13B, the inclination angles α, β, and γ measured with respect to one convex portion 20a are almost equal. The average of the three. For example, as shown in FIG. 13C, when the convex portion 20a is hemispherical, the inclination angles α, β, γ are measured for one convex portion 20a, and the average is the side surface inclination angle of the convex portion 20a1. For example, as shown in FIG. 13D, even when the convex portion 20a has two inclination angles, α, β, and γ are measured in the same manner, and the average is the side surface inclination angle of the convex portion 20a1. The second fine concavo-convex structure 60 is defined similarly.

  About the 1st fine concavo-convex structure 20, from the point which enlarges the component which contributes to extraction by optical diffraction, the convex part 20a side surface inclination angle Θ is preferably 30 degrees or more, and more preferably 35 degrees or more. On the other hand, when a crystal is grown on the optical substrate 10, voids are easily generated at the bottom of the convex portion 20a, and in order to prevent defects from being easily generated, the convex portion 20a side surface inclination angle Θ is preferably 65 degrees or less, 60 degrees or less is more preferable.

  For the second fine concavo-convex structure 60, in order to improve the upward luminance of the semiconductor light emitting device 100, the side surface inclination angle Θ is preferably 45 degrees or more, and more preferably 55 degrees or more. On the other hand, when film formation or resin filling is performed on the second fine concavo-convex structure 60, the side surface inclination angle Θ is preferably 85 degrees or less and more preferably 80 degrees or less in order to prevent the formation of voids.

  Next, a method for measuring the parameters will be described. The parameters such as the duty, the side inclination angle Θ, and the height H can be obtained for each concavo-convex structure from the above definition by observing a fine concavo-convex structure, for example, by imaging with a scanning electron microscope (SEM). it can. In this specification, an arithmetic average is taken in the local range described below, and the obtained value is set as a parameter value of the fine concavo-convex structure.

(Arithmetic mean)
When N measured values of the distribution of a certain element (variable) are x1, x2,..., Xn, the arithmetic mean value is defined by the following equation (1).

  The number N of sample points when calculating the arithmetic mean is defined as 20. The reason is set to 20 in order to obtain a sufficient statistical average when individual concavo-convex structures are arbitrarily selected within the following local range.

  Here, the local range used for observation is defined as a range of about 5 to 50 times the average pitch of the fine concavo-convex structure. For example, if the average pitch Pav_1 is 700 nm, the observation is performed in the observation range of 3500 nm to 35000 nm. For this reason, for example, a field image of 7500 nm is captured at, for example, the center position in a region having a fine concavo-convex structure, and an arithmetic average is obtained using the imaging. For example, a scanning electron microscope (SEM) can be used to capture the field image. The imaging position of the first fine concavo-convex structure may be different from the imaging position of the second fine concavo-convex structure in the in-plane direction having the fine concavo-convex structure.

  Further, when measuring the parameters of the first fine concavo-convex structure 20 and the second fine concavo-convex structure 60 from what has become the semiconductor light-emitting element 100, the package material such as the sealing material is removed, and the semiconductor light-emitting element 100 is taken out. After taking a cross-sectional image and confirming the surface having the second fine concavo-convex structure 60, the transparent conductive film 90 is formed on the layer covering the second fine concavo-convex structure 60, for example, the second semiconductor layer 50 as necessary. When the second fine concavo-convex structure 60 is provided on the upper surface of the second semiconductor layer 50, after removing the transparent conductive film 90, a surface image and a cross-sectional image of the second fine concavo-convex structure 60 are taken. Then, by removing the first semiconductor layer 30 and the layer thereon, the optical substrate 10 having the first fine concavo-convex structure 20 is obtained, and similarly, a surface image and a cross-sectional image of the first fine concavo-convex structure 20 are obtained. By imaging, the first fine irregularities It can be determined magnitude relation of the parameters forming 20 and the second fine concavo-convex structure 60 has.

  Next, materials and the like of each layer constituting the semiconductor light emitting element 100 will be described. The semiconductor light emitting device 100 according to the present embodiment is positioned above the first fine concavo-convex structure 20 and the top surface of the light emitting semiconductor layer 40 provided on the top surface of the optical substrate 10 and / or above the light emitting semiconductor layer 40. The second fine concavo-convex structure 60 formed on a part of or the entire surface (light extraction surface above the semiconductor light emitting element 100) has a shape satisfying the above range, so that the internal quantum efficiency IQE and the light extraction efficiency LEE In order to achieve the semiconductor light emitting device 100 in which both are improved, as long as this effect is exhibited, the material, state, number of layers or thickness of each semiconductor layer, material of the electrode, number of layers, arrangement or thickness, material of the light emitting semiconductor layer, The number of layers or thickness, the material of the growth substrate, the plane orientation, the thickness, and the like can be appropriately selected and are not particularly limited.

  A first semiconductor layer 30, a light emitting semiconductor layer 40, and a second semiconductor layer 50 are sequentially stacked from the bottom of the optical base material 10 having the first fine concavo-convex structure 20 formed on the upper surface thereof. The second fine concavo-convex structure 60 is provided on the upper surface of the layer 40 and / or a part of or the entire surface located above the light emitting semiconductor layer 40, thereby constituting the semiconductor light emitting device 100. Here, the semiconductor light emitting device 100 according to the present embodiment is characterized in that the emitted light generated in the light emitting semiconductor layer 40 is extracted from the second fine concavo-convex structure 60 side or the optical substrate 10. Further, the first semiconductor layer 30 and the second semiconductor layer 50 are different semiconductor layers. Here, it is preferable that the first semiconductor layer 30 planarizes the first fine concavo-convex structure 20. By providing the first semiconductor layer 30 so as to planarize the first fine concavo-convex structure 20, the performance of the first semiconductor layer 30 as a semiconductor is reflected in the light emitting semiconductor layer 40 and the second semiconductor layer 50. Therefore, the internal quantum efficiency IQE is improved. The first semiconductor layer 30 may be composed of an undoped first semiconductor layer 31 and a doped first semiconductor layer 32.

  Further, the light emitting semiconductor layer 40 and the second semiconductor layer 50 are stacked following the first semiconductor layer 30. Thereafter, a transparent conductive film 90 is provided on the second semiconductor layer 50 of the semiconductor light emitting device 100, an anode electrode 70 is provided on the upper surface of the transparent conductive film 90, and a cathode electrode 80 is provided on the upper surface of the first semiconductor layer 30. it can. The arrangement of the transparent conductive film 90, the anode electrode 70, and the cathode electrode 80 is not limited because it can be optimized as appropriate depending on the semiconductor light emitting element, but is generally provided as illustrated in FIG. In FIG. 2, the transparent conductive film 90 covers the entire second fine concavo-convex structure 60, but may be provided so as not to be partially covered. Further, as illustrated in FIG. 1, the transparent conductive film 90 may not be provided.

First semiconductor layer 30
The first semiconductor layer 30 is not particularly limited as long as it can be used as an n-type semiconductor layer suitable for a semiconductor light emitting device (LED). For example, elemental semiconductors such as silicon and germanium, and compound semiconductors such as III-V, II-VI, and VI-VI can be appropriately doped with various elements.

  The first semiconductor layer 30 and the optical substrate 10 on which the first fine concavo-convex structure 20 described later can be combined as appropriate from the viewpoint of reducing dislocations in the first semiconductor layer 30. When the flat surface of the bottom of the concave portion 20b of the first fine concavo-convex structure 20 and the plane substantially parallel to the stable growth surface of the first semiconductor layer 30 are parallel, the concave portion of the first fine concavo-convex structure 20 Since the disorder of the growth mode of the first semiconductor layer 30 in the vicinity of 20b becomes large and the dislocations in the first semiconductor layer 30 can be effectively dispersed according to the first fine concavo-convex structure 20, the internal quantum efficiency IQE Will improve. The stable growth surface is the surface with the slowest growth rate in the material to be grown.

  Further, since the first fine concavo-convex structure 20 is nano-order, the thickness necessary for flattening the first fine concavo-convex structure 20 with the first semiconductor layer 30 is reduced. For this reason, since the semiconductor layer that absorbs light from the light emitting semiconductor layer 40 is thinned, the light extraction efficiency LEE is expected to be further improved, and the first semiconductor layer 30 and the light emitting semiconductor layer 40 sequentially stacked thereon are also provided. And it becomes possible to suppress the curvature of the 2nd semiconductor layer 50, and it can be set as the semiconductor light emitting element 100 of a larger area than before. For this reason, the thickness of the first semiconductor layer 30 is preferably 5 μm or less, more preferably 4 μm or less, further preferably 3.5 μm or less, still more preferably 2.5 μm or less, and most preferably 1.5 μm or less.

-Light emitting semiconductor layer 40
The light emitting semiconductor layer 40 is not particularly limited as long as it has a light emitting characteristic as a semiconductor light emitting element (LED). For example, as the light emitting semiconductor layer 40, a semiconductor layer such as AsP, GaP, AlGaAs, InGaN, GaN, AlGaN, ZnSe, AlHaInP, or ZnO can be applied. Further, the light emitting semiconductor layer 40 may be appropriately doped with various elements according to characteristics.

Second semiconductor layer 50
The second semiconductor layer 50 is not particularly limited as long as it can be used as a p-type semiconductor layer suitable for a semiconductor light emitting device (LED). For example, elemental semiconductors such as silicon and germanium, and compound semiconductors such as III-V, II-VI, and VI-VI can be appropriately doped with various elements.

Optical substrate 10
The material of the optical substrate 10 is not particularly limited as long as it can be used as a substrate for a semiconductor light emitting device. Sapphire, SiC, SiN, GaN, W-Cu, silicon, zinc oxide, magnesium oxide, manganese oxide, zirconium oxide, manganese zinc iron oxide, magnesium aluminum oxide, zirconium boride, gallium oxide, indium oxide, lithium gallium oxide, oxidation Substrates such as lithium aluminum, neodymium gallium oxide, lanthanum strontium aluminum tantalum, strontium titanium oxide, titanium oxide, hafnium, tungsten, molybdenum, GaP, and GaAs can be used. Of these, sapphire, GaN, GaP, GaAs, SiC substrate, Si substrate, spinel substrate and the like are preferably used from the viewpoint of lattice matching with the semiconductor layer. Furthermore, it may be used alone, or may be a heterostructure substrate in which another substrate is provided on the substrate body using these. For example, a sapphire substrate having a C plane (0001) as the main surface can be used as the optical base material 10.

・ Transparent conductive film 90
In the semiconductor light emitting device 100 according to the present embodiment, the material of the transparent conductive film 90 is not particularly limited as long as it can be used as the transparent conductive film 90 suitable for the LED. For example, a metal thin film such as a Ni / Au electrode or a conductive oxide film such as ITO, ZnO, In ₂ O ₃ , SnO ₂ , IZO, or IGZO can be applied. In particular, ITO is preferable from the viewpoints of transparency and conductivity.

  Next, each process of the manufacturing method of the semiconductor light emitting device 100 according to the present embodiment will be described.

-Fine concavo-convex structure preparation process If the 1st fine concavo-convex structure 20 and the 2nd fine concavo-convex structure 60 which were demonstrated above can be formed, the preparation method will not be limited, A transfer method, a photolithographic method, a thermal lithography method, an electron beam It can be produced by a drawing method, an interference exposure method, a lithography method using nanoparticles as a mask, a lithography method using a self-organized structure as a mask, or the like. In particular, it is preferable to employ a transfer method from the viewpoint of processing accuracy and processing speed of the first fine uneven structure 20 and the second fine uneven structure 60.

  The transfer method in the present specification refers to a texture of a mold having a texture on the surface (a layer provided with the optical substrate 10 or the second fine concavo-convex structure 60 before the first fine concavo-convex structure 20 is produced). It is defined as a method including a step of transferring to That is, it is a method including at least a step of bonding a texture of a mold and an object to be processed through a transfer material and a step of peeling the mold. More specifically, the transfer method can be classified into two.

  First, the transfer material transferred to the object to be processed is used as a permanent agent. In this case, particularly in the first fine concavo-convex structure 20, the materials constituting the optical substrate 10 main body and the first fine concavo-convex structure 20 are different. The fine uneven structure remains as a permanent agent and is used as a semiconductor light emitting device. Since the semiconductor light emitting element is used for a long period of tens of thousands of hours, when the transfer material is used as a permanent agent, the material constituting the transfer material preferably contains a metal element. In particular, it is preferable to include a metal alkoxide that generates a hydrolysis / polycondensation reaction or a metal alkoxide condensate as a raw material because the performance as a permanent agent is improved.

  Secondly, there is a nanoimprint lithography method. The nanoimprint lithography method includes a step of transferring a texture of a mold onto a target object, a step of providing a mask for processing the target object by etching, and a step of etching the target object. For example, when one type of transfer material is used, first, the object to be processed and the mold are bonded via the transfer material. Subsequently, the transfer material is cured by heat or light (UV), and the mold is peeled off. Etching typified by oxygen ashing is performed on the concavo-convex structure made of a transfer material to partially expose the object to be processed. Thereafter, the object to be processed is processed by etching using the transfer material as a mask. As a processing method at this time, dry etching and wet etching can be employed. Dry etching is useful for increasing the height of the concavo-convex structure. For example, when two types of transfer materials are used, a first transfer material layer is first formed on the object to be processed using the first transfer material. Subsequently, the first transfer material layer and the mold are bonded via the second transfer material. Thereafter, the transfer material is cured by heat or light (UV), and the mold is peeled off. Etching typified by oxygen ashing is performed on the concavo-convex structure composed of the second transfer material layer to partially expose the first transfer material layer. Subsequently, the first transfer material layer is etched by dry etching using the second transfer material layer as a mask. Thereafter, after the etching, the object to be processed is processed by etching using the remaining first transfer material layer and second transfer material layer as a mask. As a processing method at this time, dry etching and wet etching can be employed. Dry etching is useful for increasing the height of the fine relief structure.

  As described above, by adopting the transfer method, the texture of the mold can be reflected on the object to be processed, so that the optical substrate 10 or the second fine concavo-convex structure having the excellent first fine concavo-convex structure 20 is provided. The semiconductor light emitting device 100 having 60 can be obtained.

  The material of the nanoimprint mold is not particularly limited, and non-flexible glass, quartz, sapphire, nickel, or flexible resin can be used. Among them, it is preferable to use a flexible mold because the transfer accuracy of the texture of the mold is improved and the accuracy of the fine uneven structure to be formed is improved.

-Semiconductor layer and transparent conductive film lamination process On the 1st fine uneven structure 20 of the optical base material 10, the 1st semiconductor layer 30, the light emitting semiconductor layer 40, the 2nd semiconductor layer 50, and the transparent conductive film 90 are formed into a film in order. The method for forming each semiconductor layer is not particularly limited, but the well-known metal organic chemical vapor deposition method (MOCVD method), molecular beam crystal growth method (MBE method), halide vapor phase epitaxy method (HVPE method), sputtering method, It can be formed by an ion plating method, an electron shower method, or the like.

  Since the first fine concavo-convex structure 20 has a nano-order structure, the thickness of the first semiconductor layer 30 for planarization can be reduced. This means that the manufacturing time and cost are reduced as compared with the conventional method. In LED manufacturing, the (MO) CVD process, which is a semiconductor crystal layer deposition process, is rate-limiting, lowering throughput and raising material costs. The ability to reduce the amount of semiconductor crystals means an improvement in throughput of the (MO) CVD process and a reduction in materials used, which is an important requirement for manufacturing.

-2nd fine concavo-convex structure 60 formation process The 2nd fine concavo-convex structure 60 differs in a formation process by the surface in which the 2nd fine concavo-convex structure 60 is provided. As shown in FIG. 1 or FIG. 2, when the second fine concavo-convex structure 60 is provided on the upper surface of the second semiconductor layer 50, after the film formation up to the second semiconductor layer 50, the second semiconductor layer is formed by, for example, the transfer method described above. The second fine concavo-convex structure 60 can be provided on the upper surface of 50. Alternatively, when the second fine concavo-convex structure 60 is provided on the upper surface of the light emitting semiconductor layer 40 as shown in FIG. 3, after the film formation up to the light emitting semiconductor layer 40, the second surface is formed on the upper surface of the light emitting semiconductor layer 40 by, for example, the transfer method described above. A fine concavo-convex structure 60 can be formed. As shown in FIG. 4, when the second fine concavo-convex structure 60 is provided on the upper surface of the transparent conductive film layer 90, after the film formation up to the transparent conductive film layer 90, the second fine concavo-convex structure 60 is made transparent by, for example, the transfer method described above. The conductive film layer 90 can be provided on the upper surface.

-Electrode formation process The anode electrode 70 and the cathode electrode 80 are formed with respect to the wafer formed into a film as mentioned above. These electrodes are formed by a known method. For example, a photoresist is formed, and photolithography is performed to pattern the semiconductor light emitting device 100. The portion not covered with the resist is etched down to the first semiconductor layer 30 by chlorine-based dry etching, and then the resist is removed. A photoresist is formed again, and photolithography is performed to pattern the electrode pad formation site. Next, a metal (Cr, Ti, Au, etc.) as an electrode pad material is formed on the entire surface by a known method such as vacuum deposition or sputtering. Thereafter, the resist and the electrode pad material formed on the resist are removed by a lift-off method, and the anode electrode 70 and the cathode electrode 80 are formed.

  The material of the anode electrode 70 and the cathode electrode 80 may be any material that can contact the semiconductor layer to which the electrodes are bonded with low resistance. The anode electrode 70 and the cathode electrode 80 may have a structure including only a pad portion. However, a wiring electrode having a grid pattern or a radial pattern continuous to the pad portion is provided to improve current diffusion in the element surface direction. You may make it make it.

-Cutting process Using a laser scrip or a laser dicer, individual change processing is performed to divide into light emitting elements.

Examples performed to confirm the effects of the present invention will be described below. The symbols used in the following description have the following meanings.
・ DACHP: Fluorine-containing urethane (meth) acrylate (OPTOOL (registered trademark) DAC HP (manufactured by Daikin Industries))
M350: trimethylolpropane (EO-modified) triacrylate (M350, manufactured by Toagosei Co., Ltd.)
・ I. 184 ... 1-hydroxycyclohexyl phenyl ketone (Irgacure (registered trademark) 184, manufactured by BASF)
・ I. 369 ... 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (Irgacure (registered trademark) 369, manufactured by BASF)
-TTB: Titanium (IV) tetrabutoxide monomer (Wako Pure Chemical Industries, Ltd.)
SH710: Phenyl-modified silicone (Toray Dow Corning)
・ 3APTMS ... 3-acryloxypropyltrimethoxysilane (KBM5103 manufactured by Shin-Etsu Silicone)
-DIBK ... diisobutyl ketone-MEK-methyl ethyl ketone-MIBK-methyl isobutyl ketone-PGME ... 1-methoxy-2-propanol-SR833 ... tricyclodecane dimethanol diacrylate (SR833 manufactured by SARTOMER)
SR368: Tris (2-hydroxyethyl) isocyanurate triacrylate (SR368 manufactured by SARTOMER)

  An optical base material having a first fine concavo-convex structure on the surface is prepared, a first semiconductor layer, a light emitting semiconductor layer, and a second semiconductor layer are sequentially stacked on the optical base material from below, and a second semiconductor layer is formed on the second semiconductor layer. After forming the fine concavo-convex structure, a semiconductor light emitting device (LED) was fabricated and the efficiency of the LED was compared. At this time, the shapes of the first fine uneven structure and the second fine uneven structure were changed.

  In the following examination, in order to produce a semiconductor light emitting device having a fine concavo-convex structure on the surface, first, (1) a cylindrical master mold is produced, and (2) the optical transfer method is applied to the cylindrical master mold. Thus, a reel-shaped resin mold was produced. (3) Thereafter, the reel-shaped resin mold was processed into a nano-processing member (nano-processing film) of an optical substrate. Subsequently, (4) using the nano-processing film, forming a mask on the optical substrate, and performing dry etching through the obtained mask, the optical substrate having the first fine concavo-convex structure on the surface A material was prepared. (5) Each semiconductor layer was laminated on the optical substrate. (6) Using a film for nano-processing, forming a mask on the second semiconductor layer, and performing dry etching through the obtained mask, a laminated semiconductor layer having a second fine concavo-convex structure on the surface Produced. (7) Thereafter, a transparent conductive film was deposited, and finally an electrode was attached to evaluate the performance.

(1) Production of cylindrical master mold A texture was formed on the surface of cylindrical quartz glass by a direct drawing lithography method using a semiconductor laser. First, a resist layer was formed on the surface of the cylindrical quartz glass by a sputtering method. Using a sputtering method, φ3 inch CuO (containing 8 atm% Si) was used as a target (resist layer) at an RF power of 100 W to form a 20 nm thick resist layer. Thereafter, the entire surface of the cylindrical quartz glass was exposed once. Subsequently, exposure was performed using a semiconductor laser having a wavelength of 405 nm while rotating the cylindrical quartz glass. Next, the resist layer after exposure was developed. The development of the resist layer was performed for 240 seconds using a 0.03 wt% glycine aqueous solution. Next, using the developed resist layer as a mask, the etching layer (quartz glass) was etched by dry etching. Dry etching was performed using SF ₆ as an etching gas under the conditions of a processing gas pressure of 1 Pa, a processing power of 300 W, and a processing time of 5 minutes. Finally, only the resist layer residue was peeled off from the cylindrical quartz glass having a texture on the surface using hydrochloric acid having a pH of 1. The peeling time was 6 minutes.

  Durasurf (hereinafter, registered trademark) HD-1101Z (produced by Daikin Chemical Industries), which is a fluorine-based mold release agent, was applied to the texture of the obtained cylindrical quartz glass, heated at 60 ° C. for 1 hour, and then room temperature. And fixed for 24 hours. Then, it wash | cleaned 3 times by Durasurf HD-ZV (made by Daikin Chemical Industries), and the cylindrical master mold was obtained.

(2) Production of reel-shaped resin mold Using the produced cylindrical master mold as a mold, the optical nanoimprint method was applied to continuously produce a reel-shaped resin mold G1. Subsequently, a reel-shaped resin mold G2 was continuously obtained by an optical nanoimprint method using the reel-shaped resin mold G1 as a template.

The material 1 shown below was apply | coated to the easily bonding surface of PET film A-4100 (Toyobo Co., Ltd .: width 300mm, thickness 100micrometer) by the micro gravure coating (manufactured by Yurai Seiki Co., Ltd.) so that it might become a coating film thickness of 5 micrometers. . Next, the PET film coated with the material 1 was pressed against the cylindrical master mold with a nip roll (0.1 MPa), and the integrated exposure under the center of the lamp was 1500 mJ / mm at a temperature of 25 ° C. and a humidity of 60%. A reel-shaped resin mold that is irradiated with ultraviolet rays using a UV exposure apparatus (H bulb) manufactured by Fusion UV Systems Japan Co., Ltd. so that it becomes cm ^2, and is continuously photocured, and the texture is transferred to the surface. G1 (length 200 m, width 300 mm) was obtained.
Material 1 ... kDACHP: M350: I. 184: I.I. 369 = 17.5 g: 100 g: 5.5 g: 2.0 g

  Next, the reel-shaped resin mold G1 was regarded as a template, and the optical nanoimprint method was applied to continuously produce the reel-shaped resin mold G2.

Material 1 was applied to an easily adhesive surface of PET film A-4100 (manufactured by Toyobo Co., Ltd .: width 300 mm, thickness 100 μm) by microgravure coating (manufactured by Yurai Seiki Co., Ltd.) so as to have a coating film thickness of 3 μm. Next, the PET film coated with the material 1 is pressed against the textured surface of the reel-shaped resin mold G1 with a nip roll (0.1 MPa), and integrated exposure under the center of the lamp at 25 ° C. and 60% humidity in the air. Ultraviolet rays were irradiated using a UV exposure apparatus (H bulb) manufactured by Fusion UV Systems Japan Co., Ltd. so that the amount was 1200 mJ / cm ^2, and photocuring was continuously performed, and the texture was transferred to the surface. A plurality of reel-shaped resin molds G2 (length 200 m, width 300 mm) were obtained.

(3) Production of Nano-Processing Film A diluent of the following material 2 was applied to the textured surface of the reel-shaped resin mold G2. Subsequently, a diluted solution of the following material 3 was applied on the textured surface of the reel-shaped resin mold G2 enclosing the material 2 inside the texture to obtain a nano-processing film.
Material 2 ... TTB: 3APTMS: SH710: I. 184: I.I. 369 = 65.2 g: 34.8 g: 5.0 g: 1.9 g: 0.7 g
Material 3 ... Binding polymer: SR833: SR368: I.I. 184: I.I. 369 = 77.1 g: 11.5 g: 11.5 g: 1.47 g: 0.53 g
Binding polymer: Methyl ethyl ketone solution of binary copolymer of 80% by mass of benzyl methacrylate and 20% by mass of methacrylic acid (solid content 50%, weight average molecular weight 56000, acid equivalent 430, dispersity 2.7)

  (2) Using a device similar to the production of the reel-shaped resin mold, the material 2 diluted with PGME was directly applied onto the texture surface of the reel-shaped resin mold G2. Here, the dilution concentration was set such that the solid content contained in the coating raw material per unit area (material 2 diluted with PGME) was 20% or more smaller than the texture volume per unit area. After coating, the material was passed through an air-drying oven at 80 ° C. for 5 minutes, and the reel-shaped resin mold G2 containing the material 2 inside the texture was wound up and collected.

  Subsequently, the reel-shaped resin mold G2 that encloses the material 2 in the texture is unwound, and (2) the material 3 diluted with PGME and MEK is used for the texture using the same device as the production of the reel-shaped resin mold. Direct coating on the surface. Here, the dilution concentration was set such that the distance between the interface between the material 2 disposed inside the texture and the coated material 3 and the surface of the material 3 was 400 nm to 800 nm. After coating, the material was passed through an air-drying oven at 80 ° C. for 5 minutes, and a cover film made of polypropylene was put on the surface of the material 3 and wound up and collected.

(4) Nano-processing of optical substrate Using the prepared nano-processing film, processing of the optical substrate was attempted. A c-plane sapphire substrate was used as the optical substrate.

The sapphire substrate was subjected to UV-O ₃ treatment for 5 minutes to remove surface particles and to make it hydrophilic. Then, the material 3 surface of the film for nano processing was bonded with respect to the sapphire base material. At this time, the sapphire substrate was bonded in a state heated to 80 ° C. Subsequently, using a high-pressure mercury lamp light source, light was irradiated through the reel-shaped resin mold G2 so that the integrated light amount was 1200 mJ / cm ² . Thereafter, the reel-shaped resin mold G2 was peeled off.

Etching using oxygen gas is performed from the material 2 side of the obtained laminate (material 2 / material 3 / substrate laminate), and the material 2 is used as a mask to nano-process the material 3, and the sapphire substrate The surface was partially exposed. Oxygen etching was performed under the conditions of a processing gas pressure of 1 Pa and a processing power of 300 W. Subsequently, reactive ion etching using BCl ₃ gas was performed from the material 2 surface side to nano-process the sapphire substrate. Etching using BCl ₃ was performed at ICP: 150 W, BIAS: 50 W, and a processing gas pressure of 0.2 Pa, and a reactive ion etching apparatus (RIE-101iPH, manufactured by Samco Corporation) was used.

  Finally, it was washed with a solution in which sulfuric acid and hydrogen peroxide solution were mixed at a weight ratio of 2: 1 to obtain a sapphire substrate having a first fine relief structure on the surface. In addition, the shape of the 1st fine concavo-convex structure produced on a sapphire base is mainly the filling rate of the material 2 of the film for nano processing, the film thickness of the material 3, the shape of the texture produced in the cylindrical master mold, It controlled suitably by the nip pressure conditions at the time of manufacturing a reel-shaped resin mold, and the process conditions of dry etching.

(5) Production of laminated semiconductor layer On the obtained sapphire base material, a low-temperature growth buffer layer of AlxGa1-xN (0 ≦ x ≦ 1) was formed as a buffer layer in a thickness of 100 mm. Next, undoped GaN was formed as an undoped first semiconductor layer, and Si-doped GaN was formed as a doped first semiconductor layer. Subsequently, a strain absorption layer is provided, and then, as a light emitting semiconductor layer, a multi-quantum well active layer (well layer, barrier layer = undoped InGaN, Si-doped GaN) is formed as a well layer with a thickness of (60 mm, 250 mm). Were alternately stacked so that there were 6 layers and 7 barrier layers. On the light emitting semiconductor layer, Mg-doped AlGaN, undoped GaN, and Mg-doped GaN were laminated as a second semiconductor layer so as to include an electroblocking layer, to obtain a laminated semiconductor layer.

(6) Formation of second fine concavo-convex structure An attempt was made to form a second fine concavo-convex structure using the produced nano-processing film for the laminated semiconductor layer laminated up to the second semiconductor layer. That is, the second fine uneven structure was formed in the second semiconductor layer.

The material 3 surface of the film for nano-processing was bonded to the second semiconductor layer of the laminated semiconductor layer. At this time, the laminated semiconductor layer was bonded in a state heated to 80 ° C. Subsequently, using a high-pressure mercury lamp light source, light was irradiated through the reel-shaped resin mold G2 so that the integrated light amount was 1200 mJ / cm ² . Thereafter, the reel-shaped resin mold G2 was peeled off.

Etching using oxygen gas is performed from the material 2 surface side of the obtained laminated body (material 2 / material 3 / laminated semiconductor layer), the material 3 is nano-processed using the material 2 as a mask, and the laminated semiconductor layer is partially Exposed to. Oxygen etching was performed under the conditions of a processing gas pressure of 1 Pa and a processing power of 300 W. Subsequently, reactive ion etching in which Cl ₂ gas and BCl ₃ gas were mixed was performed from the material 2 surface side to nano-process the laminated semiconductor layer. Etching using the gas is performed with ICP: 50 to 150 W, BIAS: 50 to 100 W, and processing gas pressure of 0.1 to 0.2 Pa, and a reactive ion etching apparatus (RIE-101iPH, manufactured by Samco Corporation). It was used. The gas ratio was a flow rate ratio of Cl ₂ / (Cl ₂ + BCl ₃ ) of 0 to 0.5.

  Oxygen etching was performed after dry etching to remove the mask and etching deposits remaining in the stacked semiconductor layer. Oxygen etching was performed under the conditions of a processing gas pressure of 1 Pa and a processing power of 300 W. The shape of the second fine concavo-convex structure formed in the laminated semiconductor layer is mainly obtained by appropriately changing the filling rate of the material 2 for the nano-processing film, the film thickness of the material 3, and the reactive ion etching conditions. Controlled.

  Then, ITO was formed into a film as a transparent conductive film, and about the semiconductor light-emitting device obtained through the electrode formation process and the cutting process, a current of 20 mA was passed between the p electrode pad and the n electrode pad, and the light emission output was measured. The light emission output ratio was set to 1 for the light emitting output of the semiconductor light emitting device not having the first fine uneven structure and the second fine uneven structure.

  In the examples, in order to improve the internal quantum efficiency IQE, a sapphire substrate having a first fine concavo-convex structure having dot-like convex portions was used. Therefore, when the first fine concavo-convex structure and the second fine concavo-convex structure were observed with a scanning electron microscope, it had a plurality of convex portions. The vacuum wavelength λ0 of the emitted light was 450 nm, and the refractive index n1 of the first semiconductor layer was 2.45. The refractive index n2 of the second semiconductor layer is assumed to be equal to the refractive index n1 of the first semiconductor layer. Similarly, the second fine concavo-convex structure had dot-like convex portions.

  The internal quantum efficiency IQE was determined from the PL intensity. The internal quantum efficiency IQE is defined by (number of photons emitted from the light emitting semiconductor layer per unit time / number of electrons injected into the semiconductor light emitting element per unit time). In this example, (PL intensity measured at 300K / 10 PL intensity measured at 10K) was adopted as an index for evaluating the internal quantum efficiency IQE.

  The output directivity is the light emission characteristics of the semiconductor light-emitting element, and the three-dimensional light emission state at 20 mA is a light distribution spectroscope (IMS5000-LED, manufactured by Asahi Spectroscopic Co., Ltd.). Measurement was performed at 360 degrees in increments of 10 degrees, and the polar angle (hereinafter referred to as the irradiance reference angle δ) at which the irradiance is half of the semiconductor light emitting element in the upward direction was examined. The irradiance in the upward direction was determined by measuring the irradiance and averaging the values obtained at points within a polar angle of 15 degrees. The smaller the irradiance reference angle δ, the higher the light distribution.

(Example 1 to Example 11)
The first fine concavo-convex structure provided on the optical base material is substantially the same, and the second fine concavo-convex structure has a duty d, a side inclination angle Θ, an average pitch Pav_2 of the second fine concavo-convex structure, and emitted light emitted from the light-emitting semiconductor layer The ratio (Pav_2 / λ2) to the second optical wavelength λ2 and the aspect ratio A were changed. The first fine concavo-convex structure was substantially conical, and the second fine concavo-convex structure was substantially frustoconical.

(Comparative Example 1 to Comparative Example 5)
As for the duty d, the internal quantum efficiency IQE, the light emission output ratio, and the output directivity are the same as those of the first to eleventh embodiments except that the second fine concavo-convex structure is larger than the first fine concavo-convex structure. investigated. The results are shown in Table 1.

  In Example 1 to Example 11, the duty of the second fine uneven structure is smaller than the duty of the first fine uneven structure, so that the light extraction efficiency is improved and the light distribution in the upward direction of the semiconductor light emitting element is strengthened. I was able to confirm.

(Example 12 to Example 24)
The average pitches Pav_1 and Pav_2 of the first fine concavo-convex structure and the second fine concavo-convex structure provided on the optical substrate were changed, and the internal quantum efficiency IQE, the light emission output ratio, and the emission directivity were examined. The first fine concavo-convex structure was substantially conical, and the second fine concavo-convex structure was substantially frustoconical.

(Comparative Example 6 to Comparative Example 12)
Regarding the duty d, the average pitches Pav_1 and Pav_2 are changed in the same manner as in Example 12 to Example 24 except that the second fine uneven structure is larger than the first fine uneven structure, and the internal quantum efficiency IQE, light emission output is changed. The ratio and output directivity were examined. The results are shown in Table 2.

  It was confirmed that the light extraction efficiency was improved and the light distribution in the upward direction of the semiconductor light emitting element was enhanced by the magnitude relationship of the duty d, regardless of the magnitude relationship between the average pitches Pav_1 and Pav_2.

(Example 25 to Example 27)
In the same manner as in Examples 1 to 24, the first fine concavo-convex structure remained substantially conical, and the shape of the second fine concavo-convex structure was changed from a substantially truncated cone shape to a substantially conical shape.

(Comparative Example 13 to Comparative Example 15)
Except that the side surface inclination angle Θ of the second fine concavo-convex structure is smaller than the side surface inclination angle Θ of the first fine concavo-convex structure, the internal quantum efficiency IQE, the light emission output ratio, and the emission are the same as those in Examples 25 to 27. The directivity was examined. The results are shown in Table 3.

  In Example 25 to Example 27, the second fine concavo-convex structure is larger than the first fine concavo-convex structure with respect to the side surface inclination angle Θ, and thus the light distribution upward of the semiconductor light emitting element is increased. It could be confirmed. In Comparative Examples 13 to 15, since the side surface inclination angle Θ of the second fine concavo-convex structure is smaller than the side surface inclination angle Θ of the first fine concavo-convex structure, the contribution to light extraction is small, and the upward light distribution It is estimated that is not strengthened.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the drawings are not limited to this, and can be appropriately changed within a range in which the effects of the present invention are exhibited.

  The present invention can be suitably applied to a semiconductor light emitting element such as a light emitting diode (LED).

DESCRIPTION OF SYMBOLS 10 Optical base material 20 1st fine uneven structure 30 1st semiconductor layer 40 Light emitting semiconductor layer 50 2nd semiconductor layer 60 2nd fine uneven structure 70 Anode electrode 80 Cathode electrode 90 Transparent conductive film 100 Semiconductor light emitting element

Claims (7)

At least an optical base material, a first semiconductor layer, a light emitting semiconductor layer and a second semiconductor layer are laminated in order from the bottom,
A first fine concavo-convex structure is formed on part or the entire upper surface of the optical substrate,
A second fine concavo-convex structure is formed on the upper surface of the light emitting semiconductor layer and / or a part of or the entire surface located above the light emitting semiconductor layer,
The semiconductor light emitting element, wherein a duty of the second fine concavo-convex structure is smaller than a duty of the first fine concavo-convex structure.   2. The semiconductor light emitting device according to claim 1, wherein a side inclination angle of the second fine concavo-convex structure is larger than a side inclination angle of the first fine concavo-convex structure.   The ratio (Pav_2 / λ2) between the average pitch Pav_2 of the second fine concavo-convex structure and the second optical wavelength λ2 of the emitted light emitted from the light emitting semiconductor layer is 1.5 or more and 5.5 or less, and the second 3. The semiconductor light emitting device according to claim 1, wherein the fine concavo-convex structure has an aspect ratio of 0.2 or more and 1 or less.   4. The semiconductor according to claim 3, wherein the second optical wavelength λ <b> 2 is obtained by dividing the vacuum wavelength λ <b> 0 of the emitted light by the refractive index n <b> 2 of the layer having the second fine concavo-convex structure on the upper surface. Light emitting element.   A ratio (Pav_1 / λ1) between an average pitch Pav_1 of the first fine uneven structure and a first optical wavelength λ1 of emitted light emitted from the light emitting semiconductor layer is 1.5 or more and 5 or less, and the first fine unevenness 5. The semiconductor light emitting device according to claim 1, wherein the aspect ratio of the structure is 0.2 or more and 1 or less.   6. The semiconductor light emitting element according to claim 5, wherein the first optical wavelength [lambda] 1 is obtained by dividing the vacuum wavelength [lambda] 0 of the emitted light by the refractive index n1 of the first semiconductor layer.   The semiconductor light emitting device according to claim 1, wherein the first semiconductor layer, the light emitting semiconductor layer, and the second semiconductor layer are GaN-based semiconductors.

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