JP2005347700A - Light emitting device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device which enhances external irradiation without leaving light in a layer of a high light absorption coefficient, and also to provide its manufacturing method. <P>SOLUTION: In the light emitting device, a sapphire substrate is lifted off from a GaN-based semiconductor layer of an LED device 1, and the light emitting device is constituted so that a glass member 11 having lower refraction factor than the sapphire substrate and having a recessed portion 11A may be joined to an n-GaN layer 13. With the constitution, the trapped light in the layer which is propagated in the n-GaN layer 13 is efficiently reflected from the recessed portion 11A to guide it to a transparent electrode 17 side, and as a result, a light takeoff capability is improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting device and a method for manufacturing the same, and more particularly to a light emitting device capable of promoting external radiation without stopping light in a layer having a large light absorption coefficient and a method for manufacturing the same.

  Conventionally, a method of manufacturing a light emitting device by growing a semiconductor crystal made of a group III nitride compound semiconductor on a base substrate such as sapphire is known. In such a light-emitting element, there is a problem that light generated in the light-emitting layer is confined in a layer having a high light absorption coefficient and is absorbed in the layer, thereby reducing external radiation efficiency.

  As a solution to such a problem, there is a light emitting element in which an uneven surface is formed on the surface of a sapphire substrate and a group III nitride compound semiconductor layer is provided thereon (see, for example, Patent Document 1).

  The light emitting device described in Patent Document 1 is formed of a group III nitride compound semiconductor on a substrate surface, and a surface of the buffer layer having a texture structure, a trapezoidal shape, or a pit shape is formed. A group III nitride compound semiconductor layer is formed on the layer.

According to the light-emitting element described in Patent Document 1, the light incident on the interface between the sapphire substrate and the group III nitride compound semiconductor layer with a large angle (light having a small angle between the interface and the light traveling direction). Even in such a case, the light can be emitted from the step surface (side surface) to the outside, and the light extraction efficiency is improved.
Japanese Patent Laying-Open No. 2003-197961 (FIG. 1, [0011])

  However, according to the light-emitting element described in Patent Document 1, the extraction of light confined in the layer (in-layer confinement light) other than the light extracted directly from the group III nitride compound semiconductor layer is uneven. Even if the processing is performed, the reflectivity of the light confined in the layer is not sufficient, and the light extraction efficiency is limited because it depends on the refractive index difference between the group III nitride compound semiconductor layer and the sapphire substrate. Further, since the group III nitride compound semiconductor layer has a large light absorption coefficient, it is attenuated and cannot be used effectively when it becomes confined light in the layer.

  Accordingly, an object of the present invention is to provide a light emitting device capable of promoting external radiation without stopping light in a layer having a large light absorption coefficient, and a method for manufacturing the same.

  In order to achieve the above object, a first invention includes a semiconductor layer including a light emitting layer and having an uneven surface, and a transparent material attached to the uneven surface side of the semiconductor layer, The material provides a light-emitting element having a refractive index lower than that of the semiconductor layer.

  In order to achieve the above object, the second invention includes a semiconductor layer including a light emitting layer and having an uneven surface, and a transparent material attached to the uneven surface side of the semiconductor layer, The light-transmitting material is characterized in that the transmissive material has an air layer corresponding to the uneven shape with the semiconductor layer.

  According to a third aspect of the present invention, there is provided a substrate preparation step for preparing a base substrate, a concavo-convex processing step for performing concavo-convex processing on the base substrate, and the base substrate subjected to the concavo-convex processing to achieve the above object. A semiconductor layer forming step of forming a semiconductor layer; a lift-off step of lifting off the base substrate from the semiconductor layer; and a transparent material that provides a transparent material on the base substrate mounting side of the semiconductor layer lifted off the base substrate There is provided a method for manufacturing a light-emitting element, including a bonding step and an electrode formation step of forming an electrode on the semiconductor layer provided with a transmissive material.

  According to a fourth aspect of the present invention, there is provided a substrate preparing step for preparing a base substrate, a semiconductor layer forming step for forming a semiconductor layer on the base substrate, and lifting off the base substrate from the semiconductor layer. A lift-off process, a concavo-convex process process in which a concavo-convex process is performed on the base substrate mounting side of the semiconductor layer lifted off the base substrate, and a transmissive material is provided on a processed surface of the semiconductor layer subjected to the concavo-convex process There is provided a method for manufacturing a light-emitting element, comprising: a transparent material bonding step; and an electrode formation step of forming an electrode on the semiconductor layer bonded with the transparent material.

  According to the present invention, the light extraction property is enhanced by changing the radiation direction of the confinement light within the semiconductor layer that remains in the semiconductor layer based on the shape of the concavo-convex portion and the refractive index of the transmissive material. External radiation can be promoted without keeping light in the layer having a large absorption coefficient.

(First embodiment)
(Configuration of LED element 1)
FIG. 1 is a longitudinal sectional view of an LED element according to the first embodiment. The face-up LED element 1 includes a glass member 11 that is a transparent material having a lower refractive index than the GaN-based semiconductor layer 100 having the light-emitting layer 14, an n-GaN layer 13 formed of a GaN semiconductor compound, n A light emitting layer 14 laminated on the -GaN layer 13, a p-GaN layer 15 laminated on the light emitting layer 14, and an n-GaN layer removed by etching from the p-GaN layer 15 to the n-GaN layer 13. 13, an n-electrode 16 provided on the p-GaN layer 15, a transparent electrode 17 provided on the p-GaN layer 15, and a p-electrode 18 provided on the transparent electrode 17.

  The formation method of the group III nitride compound 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). It can be formed by sputtering, ion plating, electron shower, or the like. Note that a light-emitting element having a homo structure, a hetero structure, or a double hetero structure can be used. Furthermore, a quantum well structure (single quantum well structure or multiple quantum well structure) can also be adopted.

The glass member 11 has a refractive index n = 1.5, a thermal expansion coefficient of 6 × 10 ⁻⁶ / ° C., and a glass point transition point of 540 ° C., and a GaN-based semiconductor compound grown on a sapphire substrate (not shown). It is separated from the sapphire substrate by being peeled off based on the laser beam irradiation, and is thermally fused to the exposed n-GaN layer 13. The glass member 11 has a recess 11 </ b> A that reflects light incident through the n-GaN layer 13 based on light emission of the light emitting layer 14 in the light extraction direction on the transparent electrode 17 side.

  The concave portion 11 </ b> A has an inverted trapezoidal shape, and is provided by transferring a convex portion provided on the n-GaN layer 13 based on thermal fusion with the n-GaN layer 13. The convex portion of the n-GaN layer 13 is formed by forming an inverted trapezoidal concave portion in advance on the sapphire substrate by etching or the like and growing a GaN-based semiconductor compound thereon. The inclined surface of the recess 11A is formed at 45 degrees with respect to the central axis A in the figure.

(Manufacturing process of LED element 1)
FIG. 2 is a diagram showing a manufacturing process of the LED element. Below, the manufacturing process of the LED element 1 is demonstrated.

(Board preparation process)
FIG. 2A is a diagram illustrating a substrate preparation process. First, a wafer-like sapphire substrate 10 serving as a base substrate is prepared.

(Rough process)
FIG. 2B is a diagram showing a concavo-convex processing step on the sapphire substrate. By etching the sapphire substrate 10, inverted trapezoidal concave portions 10 </ b> A are formed in the sapphire substrate 10 at a predetermined interval. Next, the AlN buffer layer 12 is formed on the surface of the sapphire substrate 10 on which the recess 10A is formed.

(Semiconductor layer formation process)
FIG. 2C is a diagram showing a process for forming a GaN-based semiconductor layer. An n-GaN layer 13, a light emitting layer 14, a p-GaN layer 15, and a transparent electrode 17 are sequentially provided on the AlN buffer layer 12, and then etched from the p-GaN layer 15 to the n-GaN layer 13. By removing, the n-GaN layer 13 is exposed.

(Lift-off process)
FIG. 2D is a diagram showing a lift-off process between the sapphire substrate and the GaN-based semiconductor layer. A sapphire substrate 10 on which the GaN-based semiconductor layer 100 shown in FIG. 2C is laminated is irradiated with a laser beam from the sapphire substrate 10 side over the entire surface of the wafer. The laser beam irradiated here has a wavelength that passes through the sapphire substrate and does not pass through the GaN-based semiconductor layer 100. Based on such irradiation of the laser beam, the interface between the sapphire substrate 10 and the n-GaN layer 13 is locally heated, and as a result, the sapphire substrate 10 is peeled from the n-GaN layer 13. Here, the AlN buffer layer 12 remaining on the n-GaN layer 13 side is removed based on acid cleaning.

(Glass preparation process)
FIG.2 (e) is a figure which shows the glass preparation process which prepares the glass member heat-sealed to the GaN-type semiconductor layer from which the sapphire substrate was peeled. With respect to the GaN-based semiconductor layer 100 from which the sapphire substrate 10 is lifted off in FIG. 2E, an n = 1.5 glass member 11 is disposed on the n-GaN layer 13 side.

(Glass crimping process)
FIG. 2 (f) is a diagram showing a glass crimping process for thermally fusing a glass member to the n-GaN layer 13. By hot-pressing the glass member 11 on the n-GaN layer 13, the convex portion formed on the n-GaN layer 13 is transferred to the glass member 11, thereby forming a concave portion 11 </ b> A and heat fusion. Is done.

(Electrode formation process)
FIG. 2G is a diagram showing an electrode forming process for forming an electrode. An n-electrode 16 is formed on the n-GaN layer 13 exposed by etching, and a p-electrode 18 is formed on the transparent electrode 17. After the electrodes are formed, each LED element 1 is cut with a dicer, and an insulating film (not shown) is formed on the surface excluding the electrodes. In addition, cutting | disconnection of the LED element 1 can also be performed by methods other than the cutting | disconnection by a dicer, for example, scribe.

  In order to form an LED lamp using the LED element 1 formed as described above, first, the LED element 1 is mounted on a lead formed of a copper alloy or the like, and the n-electrode 16 and the p-electrode 18 are attached. Each wire is bonded to the lead with an Au wire. Next, it is sealed with a sealing resin and packaged.

(Operation of LED element 1)
When the LED lamp lead is connected to a power source (not shown) and energized, a forward voltage is applied from the lead to the n-electrode 16 and the p-electrode 18 through the Au wire, so that holes and electrons are generated in the light emitting layer 14. The carrier recombination occurs to emit light. Of the blue light generated based on this light emission, the blue light emitted from the light emitting layer 14 toward the transparent electrode 17 is incident on the sealing resin through the transparent electrode 17 and is emitted externally from the sealing resin.

  Of the blue light radiated from the light emitting layer 14 to the n-GaN layer 13 side, the light in the critical angle range of the glass member 11 is reflected at the interface with the glass member 11 to the transparent electrode 17 side. It is guided and emitted to the outside of the LED element 1.

  Further, a part of the in-layer confined light propagating in the lateral direction (layer direction) of the n-GaN layer 13 is reflected on the transparent electrode 17 side by being incident on the concave portion 11 </ b> A provided in the glass member 11. Radiated.

(Effects of the first embodiment)
According to the first embodiment, the following effects can be obtained.
(1) Since the sapphire substrate is lifted off from the n-GaN layer 13 of the LED element 1 and the glass member 11 having a refractive index lower than that of the sapphire substrate and having the recess 11A is joined to the n-GaN layer 13, In-layer confinement light propagating in the light can be efficiently reflected by the concave portion 11A and guided to the transparent electrode 17 side, and as a result, the light extraction performance can be improved. When the sapphire substrate 10 is used, the critical angle θc based on the difference in refractive index with the n-GaN layer 13 is 1.7 (sapphire) /2.4 (GaN): θc = 45 degrees. When the member 11 is used, 1.5 (glass) /2.4 (GaN): θc = 39 degrees, and blue light that can be transmitted to the glass member 11 becomes small. For this reason, external radiation can be promoted without keeping blue light in a layer having a large light absorption coefficient.

(2) Since the sapphire substrate 10 is lifted off from the n-GaN layer 13 with a laser beam and the glass member 11 which is a transmissive material is integrated, an LED corresponding to the emission wavelength and desired light extraction performance The element 1 can be easily formed.

(3) Since a heat-deformable glass material as a permeable material is heat-sealed by hot pressing, it has excellent adhesion to the n-GaN layer 13 and can be easily joined.

  In the LED element 1 of the first embodiment, the step of forming the recess 10A on the sapphire substrate 10 and forming the GaN-based semiconductor layer 100 thereon has been described. For example, the recess is formed on the sapphire substrate 10. Alternatively, after forming the GaN-based semiconductor layer 100, the sapphire substrate 10 may be lifted off, and an uneven portion may be formed in the exposed n-GaN layer 13 by etching or the like.

(Second Embodiment)
(Configuration of LED element 1)
FIG. 3 is a longitudinal sectional view of an LED element according to the second embodiment. In the following description, parts having the same configuration and function as those of the first embodiment are denoted by common reference numerals. The face-up type LED element 1 has a configuration in which a convex portion 11B protruding toward the n-GaN layer 13 is provided on the glass member 11 instead of the concave portion 11A of the glass member 11 described in the first embodiment. This is different from the first embodiment.

  The concave portion 11B of the glass member 11 is formed by etching the sapphire substrate 10 as in the first embodiment.

(Effect of the second embodiment)
According to the second embodiment, in addition to the preferable effects of the first embodiment, the confinement light in the layer propagating in the n-GaN layer 13 is applied to the convex portion 11B protruding to the n-GaN layer 13 side. Since it becomes easy to reach | attain, the reflected light based on reflection by the convex part 11B can be guide | induced to the transparent electrode 17 side, As a result, light extraction property improves.

  In the second embodiment, as in the LED element 1 of the first embodiment, after the GaN-based semiconductor layer 100 is formed on the sapphire substrate 10 having a flat surface, the sapphire substrate 10 is lifted off, An uneven portion may be formed on the exposed n-GaN layer 13 by etching or the like.

(Third embodiment)
(Configuration of LED element 1)
FIG. 4 is a longitudinal sectional view of an LED element according to the third embodiment. This face-up type LED element 1 is different from the first embodiment in the configuration in which fine irregularities 11C are provided at the interface between the glass member 11 and the n-GaN layer 13 described in the first embodiment. ing.

  The concavo-convex portion 11C of the glass member 11 is irregularly and finely formed based on a roughening process, an etching process, or the like on the surface of the sapphire substrate 10.

(Effect of the third embodiment)
According to the third embodiment, the in-layer confinement light propagating in the GaN layer 13 is large because the in-layer confinement light amount in the GaN layer is large even if the uneven shape is not controlled as in the first embodiment. Can be reflected by the fine irregularities 11 </ b> C formed at the interface between the glass member 11 and the n-GaN layer 13, so that the effect of improving the light extraction property can be obtained.

  In the third embodiment, as in the LED element 1 of the first embodiment, after forming the GaN-based semiconductor layer 100 on the sapphire substrate 10 having a flat surface, the sapphire substrate 10 is lifted off, Fine irregularities may be formed on the exposed n-GaN layer 13 by etching or the like.

(Fourth embodiment)
(Configuration of LED element 1)
FIG. 5 is a longitudinal sectional view of an LED element according to the fourth embodiment. In this face-up type LED element 1, a flat glass member 11 is thermally fused to the n-GaN layer 13 described in the second embodiment, and at that time, the glass member 11 and the n-GaN layer 13 are bonded together. The configuration is different from that of the second embodiment in the configuration in which the recess 13B for forming a tapered air layer is provided in the n-GaN layer 13 at a predetermined interval.

  The recess 13B is formed in the n-GaN layer 13 corresponding to the protrusion formed in advance on the sapphire substrate, which is a base substrate when forming the GaN-based semiconductor layer 100, by surface processing such as etching. The sapphire substrate is lifted off from 13 to be exposed on the lower surface of the n-GaN layer 13.

  The glass member 11 is thermally fused to the n-GaN layer 13 so as not to block the recess 13B formed in the n-GaN layer 13.

  FIGS. 6A to 6E are diagrams showing the behavior of blue light propagating in the n-GaN layer. As shown in FIG. 6A, an air layer having a refractive index n = 1.0 is formed inside the recess 13 </ b> B formed between the glass member 11 and the n-GaN layer 13. Due to the presence of the air layer, the behavior of the blue light that propagates in the layer direction in the n-GaN layer 13 and enters the inclined surface 130 of the recess 13B is as follows.

(Behavior of the blue light _{L 1)}
Blue light L ₁ incident from obliquely downward with respect to the inclined surface 130 of the recess 13B is totally reflected at the interface with the air layer, a transparent electrode is emitted in the light extraction direction of the LED elements provided by the.

(Behavior of the blue light _{L 2)}
For even the blue light L ₂ incident from substantially horizontal direction with respect to the inclined surface 130 of the recess 13B, is totally reflected at the interface with the air layer, a transparent electrode is emitted in the light extraction direction of the LED elements provided by the .

(Behavior of the blue light _{L 3)}
Furthermore, for the blue light L ₃ incident from an obliquely upward direction with respect to the inclined surface 130 of the recess 13B, is totally reflected at the interface between the air layer, the radiation in the light-extraction direction of the LED elements is a transparent electrode is provided by the Is done.

(Behavior of the blue light _{L 4)}
Blue light L ₄ of normal incidence with respect to the inclined surface 130 of the recess 13B is led to the air-layer interface 13C without refraction, refracted downward in FIG. 6 (a), the light extraction is easy direction of light from the LED element It becomes.

  FIG. 6B is a schematic diagram showing the emission of light generated at point O in the light emitting layer of the GaN layer. Blue light emitted at an arbitrary point O of the light emitting layer is emitted in all directions. Among them, the light emitted to the light emitting element sealing material (n = 1.5) or the sapphire substrate (n = 1.7) is light emitted within a range of about 40 to 45 degrees with respect to the central axis. is there. The light emitted in the other direction becomes the confinement light in the GaN layer. And the solid angle of the direction used as a confinement light in a layer is 70% or more of the whole.

  FIG. 6C is a diagram showing a relationship of critical angles when a sapphire substrate (n = 1.7) is provided instead of the air layer in the state shown in FIG. The critical angle θc of the recess 13B with respect to the inclined surface 130 is 1.7 / 2.4: θc = 45 degrees. For this reason, out of the confined light that is not emitted from the GaN layer 13, the blue light that is incident from the range indicated by the oblique lines is totally reflected to obtain the blue light that is emitted from the GaN layer. Can do. When viewed from the solid angle A, 36% of the total, and the direction in which blue light from the direction corresponding to 50% of the confined light that is not emitted from the GaN layer 13 is emitted from the GaN layer to the outside. Blue light.

  FIG.6 (d) is a figure which shows the relationship of a critical angle when a glass member (n = 1.5) is provided instead of an air layer in the state shown to (a). The critical angle θc of the recess 13B with respect to the inclined surface 130 is 1.5 / 2.4: θc = 40 degrees. Further, when viewed at the solid angle A, 43% of the total, and for the confinement light in the layer, the blue light from the direction corresponding to 60% of the light may be converted into the blue light in the direction of external emission from the GaN layer. It becomes possible.

  FIG. 6 (e) is a diagram showing the relationship of the critical angle in the case of an air layer. The critical angle θc of the recess 13B with respect to the inclined surface 130 is 1.0 / 2.4: θc = 24.6 degrees. Further, when viewed at a solid angle A, 56% of the total, and for the confinement light in the layer, blue light from the direction corresponding to 79% of the light may be converted into blue light in the direction of external emission from the GaN layer. It becomes possible.

(Effect of the fourth embodiment)
According to the fourth embodiment, since the recess 13B is provided between the glass member 11 and the n-GaN layer 13 and the air layer is formed therein, much of the blue light incident on the inclined surface 130 of the recess 13B. Can be guided to the transparent electrode side based on total reflection. Further, the blue light incident on the critical angle range is incident on the glass member 11 by changing the radiation direction toward the glass member 11 by the air layer, reflected on the bottom surface of the glass member 11 and guided to the transparent electrode side. Therefore, it is possible to efficiently extract light from the GaN-based semiconductor layer together with the total reflected light.

(Fifth embodiment)
(Configuration of LED element 1)
FIG. 7 is a longitudinal sectional view of an LED element according to the fifth embodiment. This face-up type LED element 1 is formed by thinning the glass member 11 of the LED element 1 described in the fourth embodiment and thermally fusing it to the n-GaN layer 13. In the configuration in which the heat-dissipating copper member 22 is provided via the Mo foil 21 for reducing the difference in thermal expansion coefficient between the Ag reflective layer 20 having a high reflectivity and the Ag reflective layer 20. This is different from the embodiment.

  The Ag reflection layer 20 is formed by depositing Ag in a thin film by a vapor deposition method.

(Effect of 5th Embodiment)
According to the fifth embodiment, since the n-GaN layer 13 and the Ag reflection layer 20 are bonded without directly contacting each other through the thinned glass member 11, the n-GaN layer 13 is confined in the layer. Light does not directly enter the Ag reflection layer 20, thereby improving the light extraction property to the transparent electrode without causing absorption loss. That is, although a high reflectance Ag is propagated in the thin GaN layer, a large absorption loss occurs due to the repetition of many reflections. Since propagation within the GaN layer can be achieved, absorption loss during reflection can be eliminated. Moreover, the heat dissipation to the copper member 22 is improved by the thinned glass member 11.

(Sixth embodiment)
(Configuration of LED element 1)
FIG. 8 is a longitudinal sectional view of an LED element according to the sixth embodiment. In the face-up type LED element 1, the thin glass member 11 and the Ag reflection layer 20 described in the fifth embodiment are arranged in the recess 13B provided in the n-GaN layer 13 of the LED element 1, and further, The configuration in which the copper member 22 is fixed via the solder layer 23 is different from that of the fifth embodiment.

(Effect of 6th Embodiment)
According to the sixth embodiment, since the high-reflectance Ag reflecting layer 20 is disposed in the recess 13B of the n-GaN layer 13, in addition to the preferable effect of the fifth embodiment, the layer incident on the recess 13B The internal confinement light is reflected and can be efficiently extracted to the transparent electrode side, and the blue light transmitted through the glass member 11 can also be reflected by the Ag reflection layer 20 and reflected to the transparent electrode side. The light extraction property with respect to the confinement light in the GaN layer 13 can be improved.

  FIG. 9 is a longitudinal sectional view showing a modification of the LED element of the sixth embodiment. In this modification, the n-GaN layer 13 is joined to an Ag reflective layer 20 having a high reflectivity. Thus, even if it is the structure which does not provide the glass member 11, blue light can be efficiently taken out to the transparent electrode side. Further, by not providing the glass member 11, the number of manufacturing steps can be reduced, and the LED element 1 can be reduced in thickness while being effective for cost reduction.

(Seventh embodiment)
FIG. 10 shows a flip-chip type LED element according to the seventh embodiment, wherein (a) is a longitudinal sectional view and (b) is a diagram showing the behavior of blue light in an n-GaN layer. The LED element 1 is formed of a glass member 11 which is a transparent material having a lower refractive index (n = 1.9) than a semiconductor layer having a light emitting layer as shown in FIG. The GaN layer 13, the light emitting layer 14 stacked on the n-GaN layer 13, the p-GaN layer 15 stacked on the light emitting layer 14, and the p-GaN layer 15 to the n-GaN layer 13 are removed by etching. The n-electrode 16 provided on the n-GaN layer 13 and the p-electrode 19 provided on the p-GaN layer 15 are provided.

  The light emitting layer 14 is formed by growing a GaN-based semiconductor on a sapphire substrate (not shown) as a base substrate on which the GaN-based semiconductor layer 100 is grown. Further, a concave portion 13B having a shape (cylindrical shape) corresponding to the convex portion provided on the sapphire substrate during crystal growth is formed in the n-GaN layer 13. The recesses 13B can be provided in the n-GaN layer 13 in an array such as a lattice shape or a staggered shape.

  In the light emitting layer 14, the sapphire substrate is lifted off from the n-GaN layer 13 based on the irradiation of the laser beam irradiated from the sapphire substrate side, and the glass member 11 is thermally fused to the n-GaN layer 13 instead. An air layer is formed between the heat-fused glass member 11 and the n-GaN layer 13 according to the shape of the recess 13B. In addition, after performing this process in a wafer state, processes such as electrode formation and dicing are performed.

  In the n-GaN layer 13, an air layer having a refractive index n = 1.0 is formed inside by the recess 13 </ b> B formed between the glass member 11 and the n-GaN layer 13 as shown in FIG. . Due to the presence of this air layer, the behavior of blue light propagating in the layer direction through the n-GaN layer 13 is as follows.

(Behavior of blue light L ₁ , L ₁ ′)
Blue light incident from the GaN layer 13 to the glass member 11 at an angle that does not cause total reflection enters the side surface of the recess 13B at an angle greater than the critical angle. Blue light L ₁ incident at larger becomes than the critical angle to the side face of the recess 13B is totally reflected at the interface between the air layer. The blue light L ₁ is radiated outside through the glass member 11 by being reflected again upward p- electrode 19 shown in (a). Further, the blue light L ₁ ′ from the n-GaN layer 13 toward the glass member 11 is also totally radiated through the glass member 11 by being totally reflected at the interface with the air layer. Since the side surface of the recess 13 </ b> B is a substantially vertical surface, blue light incident at an angle that does not cause total reflection from the GaN layer 13 to the glass member 11 does not undergo total reflection from the GaN layer 13 to the glass member 11. This is because the blue light incident at an angle remains.

(Behavior of blue light L ₂ , L ₂ ′)
Blue light L ₂ incident from an obliquely upward direction with respect to the side face of the recess 13B, by changed radiation direction vertical side passes through the interface between the air layer at the interface between the n-GaN layer 13 p- The light is reflected by the electrode 19, passes through the n-GaN layer 13, changes the radiation direction again at the interface with the air layer, enters the glass member 11, and is externally radiated from the glass member 11. Further, the blue light L ₂ ′ incident from the n-GaN layer 13 to the interface with the air layer obliquely from below is changed in the radiation direction further upward at the interface between the air layer and the glass member 11, and is applied to the glass member 11. Incident light is emitted from the glass member 11 to the outside.

(Behavior of blue light L ₃ , L ₃ ′)
Blue light L ₃ incident from an oblique upper direction nearly horizontal to the side face of the recess 13B is the n-GaN layer 13 side at the interface between the air layer can change the radial direction, yet the n-GaN layer 13 When the radiation direction is changed to the vertical direction side at the interface, the light is reflected by the p-electrode 19, passes through the n-GaN layer 13, enters the glass member 11, and is emitted from the glass member 11 to the outside. Further, the blue light L ₃ ′ which is incident substantially horizontally and slightly obliquely upward from the n-GaN layer 13 to the interface with the air layer has its radiation direction changed further upward at the interface between the air layer and the glass member 11, so that the glass The light enters the member 11 and is emitted from the glass member 11 to the outside.

(Effect of 7th Embodiment)
According to the seventh embodiment, the blue light incident on the recess 13 </ b> B of the n-GaN layer 13 changes the radiation direction to the glass member 11 side or the p-electrode 19. Also, the light extraction property can be improved.

  However, in this case, unlike the case where the face-up type LED element 1 is used in the first to sixth embodiments and the interface reflection is used, the semiconductor layer can be easily taken out to the glass member 11. Here, interfacial refraction is utilized. For this reason, the glass member 11 can obtain a larger effect by using the sapphire formed as it is as it is by making the refractive index higher than n = 1.7 of the original substrate sapphire.

  Note that in the flip-chip type LED element, since no electrode is present on the light extraction surface side, it is advantageous to extract light from the light emitting element to the outside other than the meaning of light extraction from the high refractive index medium.

  In the seventh embodiment, the air layer corresponding to the shape of the recess 13B is formed. However, the light extraction effect can be obtained without the air layer. Also in this case, it is desirable that the refractive index of the glass member 11 is large as described above. Although the configuration in which the concave portion 13B is cylindrical has been described, it may have other shapes such as a quadrangular prism shape or a hexagonal prism shape.

  Moreover, it is good also as a cone, a pyramid shape, etc. as another shape. In this case, the behavior of the light totally reflected on the side surface of the recess 13B is not the same, but if the refractive index of the glass member 11 is larger than that of sapphire, the GaN layer and the sapphire substrate are formed in a flat state. Light that cannot be externally reflected from the GaN layer, or light that cannot be externally reflected from the interface between the GaN layer and the sapphire substrate that are formed in the same shape, and the sapphire substrate can be emitted externally, and a light extraction effect can be obtained.

  Further, the recess 13B may be formed by dry etching or the like after the planar sapphire substrate is lifted off.

  In the first to seventh embodiments, the LED element having the semiconductor layer made of GaN has been described. However, other materials such as GaAs and AlInGaP may be used. In addition, the sapphire substrate has been described as being lifted off. However, if the epi layer and the substrate have the same refractive index, the substrate does not necessarily have to be removed, and the substrate may be directly processed to be uneven.

It is a longitudinal cross-sectional view of the LED element which concerns on 1st Embodiment. It is a figure which shows the manufacturing process of an LED element, (a) is a figure which shows a board | substrate preparation process, (b) is a figure which shows the uneven | corrugated processing process to a sapphire substrate, (c) is formation of a GaN-type semiconductor layer The figure which shows a process, (d) is a figure which shows the lift-off process of a sapphire substrate and a GaN-type semiconductor layer, (e) prepares the glass member heat-sealed to the GaN-type semiconductor layer from which the sapphire substrate was peeled off The figure which shows the glass preparatory process to perform, (f) is a figure which shows the glass crimping | compression-bonding process of thermally fusing a glass member to the n-GaN layer 13, (g) is a figure which shows the electrode formation process which forms an electrode. . It is a longitudinal cross-sectional view of the LED element which concerns on 2nd Embodiment. It is a longitudinal cross-sectional view of the LED element which concerns on 3rd Embodiment. It is a longitudinal cross-sectional view of the LED element which concerns on 4th Embodiment. (A) to (e) are diagrams showing the behavior of blue light propagating in the n-GaN layer. It is a longitudinal cross-sectional view of the LED element which concerns on 5th Embodiment. It is a longitudinal cross-sectional view of the LED element which concerns on 6th Embodiment. It is a longitudinal cross-sectional view which shows the modification of the LED element of 6th Embodiment. FIG. 10 shows a flip-chip type LED element according to a seventh embodiment, where (a) is a longitudinal sectional view and (b) is a diagram showing the behavior of blue light in an n-GaN layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, LED element 10, Sapphire substrate 10A, Concave part 11, Glass member 11A, Concave part 11B, Convex part 11C, Concave-convex part 12, AlN buffer layer 13, n-GaN layer 13B, Concave part 13C, Air layer interface 14, Light emitting layer 15 , P-GaN layer 16, n-electrode 17, transparent electrode 18, p-electrode 19, p-electrode 20, Ag reflection layer 21, Mo foil 22, copper member 23, solder layer 100, GaN-based semiconductor layer 130, inclined surface

Claims (11)

A semiconductor layer including a light emitting layer and having an uneven surface;
A transparent material attached to the uneven surface side of the semiconductor layer,
The light-emitting element, wherein the transparent material has a lower refractive index than the semiconductor layer. A semiconductor layer including a light emitting layer and having an uneven surface;
A transparent material attached to the uneven surface side of the semiconductor layer,
The light-emitting element, wherein the transmissive material has an air layer corresponding to a concavo-convex shape between the semiconductor layer and the semiconductor layer.   The light-emitting element according to claim 1, wherein the transparent material is a glass material.   4. The light emitting device according to claim 1, wherein the semiconductor layer has the uneven surface formed by etching. 5.   5. The light emitting device according to claim 1, wherein the semiconductor layer is formed on the substrate on which the uneven surface is formed, and then lifted off the substrate. 6.   The light emitting device according to any one of claims 1 to 5, wherein the semiconductor layer is a GaN-based semiconductor layer formed on a sapphire substrate.   The light-emitting element according to claim 5, wherein the transparent material has a refractive index lower than that of a substrate having a concavo-convex surface or a sapphire substrate.   The light-emitting element according to claim 5, wherein the transparent material has a refractive index higher than that of a substrate having an uneven surface or a sapphire substrate. A substrate preparation step of preparing a base substrate;
An unevenness processing step for applying unevenness to the base substrate;
A semiconductor layer forming step of forming a semiconductor layer on the base substrate subjected to the uneven processing;
A lift-off step of lifting off the base substrate from the semiconductor layer;
A transparent material bonding step of providing a transparent material on the base substrate mounting side of the semiconductor layer lifted off the base substrate;
An electrode formation step of forming an electrode on the semiconductor layer provided with a transmissive material.   10. The method for manufacturing a light-emitting element according to claim 9, wherein in the semiconductor layer forming step, a GaN-based semiconductor layer as the semiconductor layer is formed on a sapphire substrate as the base substrate on which the unevenness processing has been performed. . A substrate preparation step of preparing a base substrate;
A semiconductor layer forming step of forming a semiconductor layer on the base substrate;
A lift-off step of lifting off the base substrate from the semiconductor layer;
A concavo-convex processing step of performing concavo-convex processing on the base substrate mounting side of the semiconductor layer lifted off the base substrate;
A permeable material joining step of providing a permeable material on the processed surface of the semiconductor layer that has been subjected to the uneven processing;
An electrode forming step of forming an electrode on the semiconductor layer bonded with a transparent material.

Images