TW201810713A - Light-emitting device - Google Patents

Abstract

This application discloses a light-emitting device. The light-emitting device comprises: a substrate; a light-emitting stack which emits an infrared light on the substrate, wherein a wavelength of the infrared light is longer than 900 nm; a window layer composed of AlGaInP series material disposed between the substrate and the light-emitting stack; and an electrode on the light-emitting stack, and a pattern of the electrode comprises circle or mesh on the top view of the light-emitting device.

Description

Light-emitting element

The present invention relates to light-emitting elements, and more particularly to infrared light-emitting elements.

Light-Emitting Diode (LED) has good optoelectronic properties such as low energy consumption, low heat generation, long operating life, shock resistance, small volume, fast response speed, and stable wavelength of output light, so it is suitable for various applications.

Infrared LEDs (IR LEDs) are used more and more widely, from traditional applications to remote controls and monitors, and more recently to smart phones and touch panels. Because each touch panel uses a relatively large amount of infrared light-emitting diodes, it is required to be lower in price than other applications, and it is necessary to reduce the cost of the infrared light-emitting diodes.

1 is a cross-sectional view of a conventional infrared light-emitting device. As shown in FIG. 1, the light-emitting element includes a permanent substrate 101, and a light-emitting layer 102, a metal reflective layer 103, The barrier layer 104, and a bonding structure 105. In addition, a first electrode 106E1 and its extension electrode 106E1' are disposed on the light emitting layer 102, and a second electrode 106E2 is disposed on the permanent substrate 101. The first electrode 106E1 and its extension electrode 106E1' and the second electrode 106E2 are used to transfer current. The light-emitting layer 102 emits light in an infrared band. In the process of the conventional infrared light-emitting device, the light-emitting laminate 102 is originally grown on a growth substrate (not shown), and the bonded structure 105 is used to bond the originally separated light-emitting laminate 102 and the permanent substrate 101. Before the two are joined, the metal reflective layer 103 is formed on the light-emitting layer 102 and then bonded. However, as described above, in a specific application, for example, when the application of the touch panel requires low cost, the bonding process and the metal reflective layer 103 are the main causes of high cost. In addition, in the application of the touch panel, the preferred side light is also required to achieve a large light exit angle. It has been found in practical applications that the above-mentioned conventional infrared light-emitting elements are difficult to meet the requirements of this aspect.

The invention discloses a light-emitting element comprising: a substrate; a light-emitting layer is arranged above the substrate to emit an infrared wavelength light having a wavelength of more than 900 nm; and a window layer composed of a material of the AlGaInP series. Between the substrate and the light-emitting layer; and an electrode on the light-emitting layer, and the pattern of the electrode comprises a circular or grid shape from the upper side of the light-emitting element.

The invention discloses a light-emitting element comprising: a substrate; and a window layer and a light-emitting layer are disposed on the substrate in a stacking direction, the window layer is located between the substrate and the light-emitting layer, wherein the window The layer is composed of a material of the AlGaInP series; wherein the light-emitting layer has a surface away from the substrate and perpendicular to the stacking direction, and the light-emitting element emits a light outward from the surface.

Fig. 2 is a view showing a light-emitting element of a first embodiment of the present invention. As shown in FIG. 2, the light-emitting element comprises: a substrate 20; a light-emitting layer 23 is disposed above the substrate 20 to emit an infrared (IR) wavelength; and a semiconductor window layer 22 is composed of a material of the AlGaInP series. Located between the substrate 20 and the light emitting laminate 23. Among them, the substrate 20 includes, for example, a gallium arsenide (GaAs) substrate. The infrared (IR) wavelength described above is between about 750 nm and 1100 nm. In one embodiment, the infrared (IR) wavelength is greater than 900 nm, such as 940 nm. The semiconductor window layer 22 is a single layer structure and is in direct contact with the light emitting laminate 23. After the semiconductor window layer 22 is formed in the process, the type or ratio of the gas to be introduced can be adjusted on the same machine to form the light-emitting laminate 23. In one embodiment, the semiconductor window layer 22 comprises (Al _x Ga _1-x ) _0.5 In _0.5 P , where x is 0.1 to 1. It should be noted that the light emitting laminate 23 has a first refractive index n ₁ , and the semiconductor window layer 22 has a second refractive index n ₂ , and the first refractive index n _{1 is} greater than the second refractive index n _{2 by} at least 0.2 or more. Therefore, the light of the infrared wavelength emitted by the light-emitting layer 23 travels between the light-emitting layer 23 and the semiconductor window layer 22 from a high refractive index to a low refractive index, and the first refractive index n of the light-emitting layer 23 is added. _{1 is} different from the second refractive index n ₂ of the semiconductor window layer 22, so that the infrared wavelength light emitted by the light-emitting layer 23 is easily totally reflected in the semiconductor window layer 22, that is, the semiconductor window layer 22 provides a single layer structure. The mirror function, and provides a better lateral reflection function relative to a generally distributed Bragg reflection structure (DBR). Generally, the distributed Bragg reflection structure (DBR) requires dozens of layers to achieve a certain degree of reflectivity, and its reflection function is limited to a certain range of forward direction, generally 0 to 17 degrees of light with the normal of the reflection structure. In this embodiment, only the semiconductor window layer 22 of a single layer structure can reflect light of 50 degrees to 90 degrees with the normal line of the semiconductor window layer 22, thereby providing better side light to form a larger light exit angle, and As the light extraction is improved, the overall luminous power is thus increased. In the actual test, the light-emitting elements emitting 850 nm and 940 nm are respectively tested. The light-emitting layer 23 of the embodiment of the present invention uses aluminum gallium arsenide (AlGaAs) in the first electrical semiconductor layer 231, and has a first refractive index n ₁ . 3.4, the semiconductor window layer 22 adopts (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P, has a second refractive index n _{2 of} about 2.98, and the difference in refractive index value is about 0.42, which is the same as other conditions but only the semiconductor window layer 22 is changed to arsenic. Compared with the light-emitting element of aluminum gallium (AlGaAs) (refractive index of about 3.4), the light-emitting power of the 850 nm light-emitting element of the embodiment of the present invention is increased from 4.21 mW to 4.91 mW, which is increased by about 17%; The luminous power of the component is increased from 5.06 mW to 5.27 mW, an increase of about 4%. In addition, the semiconductor window layer 22 is in direct contact with the light-emitting layer 23 in a process or cost, and has a single layer structure, so that the process is more simplified and the cost is lower than that of the general distributed Bragg reflection structure. In terms of thickness, in one embodiment, the thickness of the semiconductor window layer 22 is less than 1 μm for good reflection.

The light emitting layer 23 includes a first electrical semiconductor layer 231 on the semiconductor window layer 22; an active layer 232 on the first electrical semiconductor layer 231; and a second electrical semiconductor layer 233 on the active layer 232. The first electrical semiconductor layer 231 is in direct contact with the semiconductor window layer 22. The first electrical semiconductor layer 231, the active layer 232, and the second electrical semiconductor layer 233 are formed of a III-V material. The first electrical semiconductor layer 231 and the second electrical semiconductor layer 233 are electrically different, for example, the first electrical semiconductor layer 231 is an n-type semiconductor layer, and the second electrical semiconductor layer 233 is a p-type semiconductor layer, which is applied. In the external power supply, the first electrical semiconductor layer 231 and the second electrical semiconductor layer 233 respectively generate carriers (electrons/holes) and recombine in the active layer 232 to generate light. In an embodiment, the first electrical semiconductor layer 231 is doped with tellurium (Te) or selenium (Se). In one embodiment, the active layer 232 comprises a multiple quantum well structure (MQW) comprising a plurality of barrier layers, such as barrier layers 232b ₁ , 232b ₂ , . . . 232b _n , and one or more a well layer, such as well layer 232w ₁ , 232w ₂ , ... 232w _n-1 , there is a well layer between two adjacent barrier layers, for example, a well layer 232w between two adjacent barrier layers 232b ₁ and 232b _{2 1} . The barrier layer closest to the first electrical semiconductor layer 231 (ie, the barrier layer 232b ₁ ) and the barrier closest to the second electrical semiconductor layer 233 of the plurality of barrier layers 232b ₁ , 232b ₂ , . . . 232b _n The layer (i.e., barrier layer 232b _n ) does not contain phosphorus (P), and the remaining barrier layers (barrier layers 232b ₂ , ... 232b _n-1 ) contain phosphorus (P). In one embodiment, the well layers 232w ₁ , 232w ₂ , . . . 232w _n-1 comprise indium gallium arsenide (InGaAs), wherein the indium content is between about 2% and 30% and is dependent on the wavelength of light that the light-emitting stack 23 is intended to emit. Adjust to reach the aforementioned range of infrared rays. Since the well layers 232w ₁ , 232w ₂ , ... 232w _n-1 contain indium (In), the lattice constant becomes large, and the above barrier layers (barrier layers 232b ₂ , ... 232b _n-1 ) contain phosphorus ( P) The lattice constant can be made smaller to adjust the overall lattice constant back to the appropriate range. In an embodiment, the barrier layers 232b ₂ , . . . 232b _n-1 include, for example, aluminum gallium arsenide (AlGaAsP). As described above, the barrier layer (barrier layer 232b ₁ ) closest to the first electrical semiconductor layer 231 and the barrier layer (block layer 232 b _n ) closest to the second electrical semiconductor layer 233 do not contain phosphorus (P). The thicker barrier layer 232b ₁ and the barrier layer 232b _n may be adjacent to the adjacent first electrical semiconductor layer 231 and second electrical semiconductor layer 233. The dopant in the middle has a better diffusion barrier effect. In an embodiment, the barrier layer 232b ₁ and the barrier layer 232b _n include, for example, aluminum gallium arsenide (AlGaAs).

The light emitting device of the first embodiment of the present invention further includes a buffer layer 21 between the substrate 20 and the semiconductor window layer 22, and the buffer layer 21 is doped with germanium (Si), such as gallium arsenide (GaAs) doped with germanium (Si). . As described above, the first electrical semiconductor layer 231 is doped with germanium (Te) or selenium (Se), and the buffer layer 21 is doped with germanium (Si), so that the light-emitting element has more adjustment flexibility in the process. For example, the adjustment of the lattice constant. In addition, the light-emitting element of the first embodiment of the present invention further includes a side light extraction layer 24 on the light-emitting layer 23, a contact layer 25 on the lateral light extraction layer 24, and a first electrode 26. On the contact layer 25, a second electrode 27 is disposed on the substrate 20. The lateral light extraction layer 24 facilitates light extraction, particularly because the thickness of the side increases the side light, so the thickness can be relatively thick, for example, from about 5 μm to 30 μm. In one embodiment, the lateral light extraction layer 24 It contains gallium arsenide (GaAs) doped with zinc (Zn) and has a thickness of about 10 μm. Contact layer 25 is used to form an ohmic contact with first electrode 26 thereon to reduce the resistance value. In one embodiment, contact layer 25 comprises zinc (Zn) doped gallium arsenide (GaAs). The lateral light extraction layer 24 and the contact layer 25 are similarly doped with zinc (Zn) doped gallium arsenide (GaAs), which simplifies the configuration of the machine on the process, but it should be noted that the lateral light extraction layer 24 and the contact layer The function of 25 is different. To form an ohmic contact, the zinc (Zn) content in the contact layer 25 is much larger than the zinc (Zn) content of the lateral light extraction layer 24 to form an ohmic contact. The first electrode 26 may be provided with an extension electrode 26a to facilitate current spreading. It should be noted that when the infrared wavelength light emitted by the light-emitting layer 23 travels toward the substrate 20, there may still be some total reflection in the semiconductor window layer 22. As described above, in a specific application, a larger angle of light extraction may be required. Therefore, as shown in the figure, in the embodiment, the second electrode 27 is a patterned electrode. For a detailed description, please refer to FIG. 3 . 4, when viewed from a top view, the pattern of the second electrode 27 may be, for example, a mesh as shown in FIG. 3, and FIG. 3 shows that a substrate 20 of gallium arsenide (GaAs) is formed. a grid-like metal (GeAu) second electrode 27; or as shown in FIG. 4, the pattern of the second electrode 27 may be a plurality of circles, and FIG. 4 shows that a gallium arsenide (GaAs) substrate 20 is formed thereon. a plurality of circular-shaped sheet metal (GeAu) second electrodes 27; the second electrode 27 thus patterned forms a scattering center for light that does not totally reflect at the semiconductor window layer 22, thereby increasing scattering and making the light-emitting angle Big. In addition, it is also possible to selectively form a roughening (not shown) at the lower surface S1 of the substrate 20 without providing the second electrode 27, which also increases the scattering of light, so that the light is easily emitted from the side of the substrate 20, even the substrate. The side surface S2 of the 20 and the first surface 26 of the upper surface S3 of the light-emitting element may be roughened (not shown).

The above embodiments are merely illustrative of the principles of the invention and its advantages, and are not intended to limit the invention. Modifications and variations of the above-described embodiments can be made without departing from the spirit and scope of the invention. Therefore, the scope of the invention is as set forth in the appended claims.

101‧‧‧Permanent substrate
102‧‧‧Lighting laminate
103‧‧‧Metal reflector
104‧‧‧Barrier layer
105‧‧‧ joint structure
106E1‧‧‧First electrode
106E1'‧‧‧ (first electrode) extended electrode
106E2‧‧‧Second electrode
20‧‧‧Substrate
21‧‧‧ Buffer layer
22‧‧‧Semiconductor window layer
23‧‧‧Lighting laminate
231‧‧‧First electrical semiconductor layer
232‧‧‧Lighting layer
232b ₁ , 232b ₂ ,...232b _n ‧‧‧Barrier layer
232w ₁ , 232w ₂ ,...232w _n-1 ‧‧‧ Well
233‧‧‧Second electrical semiconductor layer
24‧‧‧ lateral light extraction layer
25‧‧‧Contact layer
26‧‧‧First electrode
26a‧‧‧ (first electrode) extension electrode
27‧‧‧second electrode
S1‧‧‧substrate lower surface
S2‧‧‧Side side
S3‧‧‧Lighting element upper surface

Figure 1 shows a conventional light-emitting element.

Fig. 2 shows a light-emitting element of a first embodiment of the invention.

Fig. 3 shows a second electrode pattern in the light-emitting element of the first embodiment of the present invention.

Fig. 4 is a view showing another pattern of the second electrode in the light-emitting element of the first embodiment of the present invention.

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Claims (10)

A light-emitting element comprising: a substrate; a light-emitting layer above the substrate to emit an infrared wavelength light having a wavelength greater than 900 nm; a window layer composed of a material of the AlGaInP series, the substrate and the substrate Between the light-emitting stacks; and an electrode on the light-emitting stack, and the pattern of the electrodes comprises a circular or grid shape from the top view of the light-emitting element. The light-emitting element of claim 1, wherein the substrate comprises gallium arsenide. The illuminating element of claim 1, wherein the electrode comprises gold. The illuminating element of claim 1, wherein the window layer comprises (AlxGa1-x)0.5In0.5P and x is between 0.1 and 1. The illuminating element of claim 1, wherein the contact layer is further disposed above the luminescent layer, and the contact layer comprises gallium arsenide. The light-emitting element of claim 5, wherein the contact layer is zinc-doped gallium arsenide. A light-emitting element comprises: a substrate; and a window layer and a light-emitting layer are disposed on the substrate in a stacking direction, the window layer is located between the substrate and the light-emitting layer, wherein the window layer is composed of AlGaInP series The material composition comprises: wherein the light emitting layer has a surface away from the substrate and perpendicular to the stacking direction, and the light emitting element emits a light outward from the surface. The light-emitting element of claim 1, wherein the window layer has a thickness of less than 1 μm. The illuminating element of claim 7, wherein the ray is infrared ray. The illuminating element of claim 7, wherein the ray wavelength is greater than 900 nm.