JP3333219B2 - Compound semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a high-brightness, high-efficiency compound semiconductor light emitting device (LED device) used for a sensor light source or the like.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional compound semiconductor light emitting device. FIG. 1 (a) is a plan view and FIG. 1 (b).
Is a side view thereof. An N-type epitaxial growth layer 2 is formed on an N-type compound semiconductor substrate 1, and a P-type epitaxial growth layer 3 is formed on the N-type epitaxial growth layer 2. These P-type epitaxial growth layer 3 and N-type epitaxial growth layer 2, a PN junction is formed. As shown in FIG. 1A, PEP (Photo Engraving Proc) is formed on the P-type epitaxial growth layer 3.
The P-type electrode 4 is patterned by the ess) process. Thereafter, a heat treatment for improving ohmic properties is performed, and the P-type electrode 4 and one end of the conductive wire 5 are connected. The other end of the conductive wire 5 is connected to the electrode terminal 6. An N-type electrode 7 is formed below the N-type compound semiconductor substrate 1, and the N-type electrode 7 is connected to a conductive stem 8. Further, the entirety is covered with a mold resin 9. The P-type electrode 4 is made of an Au-Be alloy, and the N-type electrode 7 is made of an Au-Ge alloy.

[0003]

The Au-based alloy becomes an absorber for the wavelength of light generated near the PN junction. Therefore, the P-type electrode 4 is patterned as shown in FIG.
Light is extracted from the surface exposed from the mold electrode 4. Irregularities are formed on the exposed surface of the P-type epitaxial growth layer 3 by frost processing so that light is uniformly emitted.

However, since the P-type electrode 4 serving as an absorber for the generated wavelength is provided on the surface of the P-type epitaxial growth layer 3 as a radiation surface of the light generated near the PN junction, the area of the electrode 4 depends on the area of the electrode 4. There is a problem that the luminous efficiency and the luminance are affected.

In order to improve the above problem, it is conceivable to reduce the area of the P-type electrode. However, since the carrier injection condition near the electrode and the carrier injection condition around the electrode are different, uneven light emission may occur near the PN junction, or light may only emit near the electrode.

It is also conceivable to reduce the thickness of the P-type electrode. In this case, the exposed area of the P-type epitaxial growth layer was kept constant, and the film was sufficiently thinned in a range where the same luminance as in the case where the P-type electrode 4 was thickened was obtained. But,
Since the thinned electrode has poor uniformity as a continuous film, its reliability as an electrode is low and cannot be put to practical use.

On the other hand, in the above-described conventional semiconductor light emitting device, after the P-type electrode 4 is formed on the P-type epitaxial growth layer 3, a heat treatment for improving ohmic properties is performed. At this time, a heavy metal such as Au in the P-type electrode 4 is doped into the P-type epitaxial growth layer 3, and a heavy metal diffusion region is formed in the P-type epitaxial growth layer 3. Therefore, the epitaxial growth layer 3
However, there is a problem that light is absorbed and the luminous efficiency and luminance of the compound semiconductor light emitting device are reduced.

The present invention has been made in view of the above circumstances, and has as its object to improve the uniformity of internal light emission near a PN junction and to radiate light to a P-type electrode and an impurity in a P-type epitaxial growth layer. An object of the present invention is to provide a compound semiconductor light emitting device capable of improving luminous efficiency and luminance without being absorbed by light.

[0009]

In order to solve the above-mentioned problems, the present invention provides a first epitaxial growth layer of a first conductivity type provided on a compound semiconductor substrate by epitaxial growth, and a first epitaxial growth layer of the first conductivity type. A second epitaxial growth layer of a second conductivity type, which is provided on the second epitaxial growth layer and has an unevenness on the surface; and an oxide having a transmittance of 50% or more with respect to the emission wavelength provided on the entire surface of the second epitaxial growth layer. And a first transparent electrode made of a material or a polymer-based material and an emission wavelength provided below the compound semiconductor substrate.
A second transparent electrode made of an oxide having a transmittance of 50% or more, and the second epitaxial growth layer has an impurity concentration of 1 × on a surface in contact with the first transparent electrode.
10 ¹⁹ atoms / cm ³ or less, and the impurity concentration of the surface of the compound semiconductor substrate on the side in contact with the first epitaxial growth layer is set to 1 × 10 ¹⁹ atoms / cm ³ or less.

[0010]

According to the present invention, a second conductive type second epitaxial growth layer is provided on a first conductive type first epitaxial growth layer. Since the first electrode of the second conductivity type having a transmittance of 50% or more with respect to the emission wavelength is provided on the second epitaxial growth layer, light absorption by the first electrode can be suppressed. Further, the second epitaxial growth layer has an impurity concentration of 1 × 10 ¹⁹ atoms / cm ³ on the surface in contact with the first electrode. It is as follows. Therefore, light absorption by impurities in the second epitaxial growth layer and the compound semiconductor substrate is suppressed. In addition, since the first electrode is provided on the entire surface of the second epitaxial growth layer, the uniformity of internal light emission near the junction between the first epitaxial growth layer and the second epitaxial growth layer is improved.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 2A to 2F show AlGaAs.
3 illustrates a process for manufacturing an s / GaAs-based infrared light emitting device. First, the P-type GaAs substrate 10 has a concentration of 1 × 10 ^18.
atoms / cm ³ Of Si (silicon) is doped. As shown in FIG. 2B, the P-type GaAs substrate 10 has a concentration of 1 × 10 ¹⁸ atoms / cm ^3. A P-type AlGaAs epitaxial growth layer 11 doped with Si is formed. The thickness of the epitaxial layer 11 is 50 to 100 μm.
m. On top of this epitaxial layer 11, FIG.
As shown in (c), the concentration is 5 × 10 ¹⁸ atoms / cm ³ S
An N-type AlGaAs epitaxial growth layer 12 doped with i is formed, and the thickness of the epitaxial layer 12 is about 50 to 100 μm. The epitaxial layer 1
A PN junction is formed at the junction surface between the semiconductor device 1 and the epitaxial layer 12. On the surface of the epitaxial layer 12, FIG.
As shown in FIG. 3D, the unevenness 13 is formed by the frost process. On the N-type epitaxial layer 12, FIG.
As shown in (e), a thickness of 5% when Sn is doped at a concentration of 3%.
A 2000 Å In ₂ O ₃ layer 15 is deposited by sputtering. The In ₂ O ₃ layer 15 forms an upper transparent electrode 16 having a transmittance of 50% or more with respect to the emission wavelength. The P-type GaAs de of Zn as shown in FIG. 2 (f) below the substrate 10 at a concentration of 5% - In ₂ O ₃ layer 17 having a thickness of 1μm was flop is deposited by sputtering, the In ₂ O _The lower transparent electrode 18 is formed by the _three layers 17. Light-emitting element 1 thus configured
9 is cut into pellets 20 of 300 μm square.

FIG. 3A is a plan view showing an AlGaAs / GaAs infrared light emitting device, and FIG. 3B is a side view thereof. One end 22 of a conductive wire 21 made of Au or the like is connected to the upper transparent electrode 16 of the light emitting element 19 cut into a pellet 20 of 300 μm square, and the other end 23 of the conductive wire 21 is an electrode terminal 24. Connected to. Lower transparent electrode 1 in light emitting element 19
To 8, one end 26 of a conductive stem 25 is connected by a conductive mounting material (not shown), for example, an Ag paste, and the entire light emitting element 19 is covered with a light-transmitting mold resin 29. The other end 27 of the conductive stem 25 protrudes from the translucent mold resin 29.

According to the above embodiment, the upper and lower transparent electrodes 16 and 18 are formed by the In ₂ O ₃ layers 15 and 17 having a transmittance of 50% or more with respect to the emission wavelength. For this reason, the light emitted from the N-type AlGaAs epitaxial growth layer 12 is hardly absorbed by the upper transparent electrode 16, and the luminous efficiency and the luminance can be improved. In addition, since the unevenness 13 is formed on the surface of the N-type AlGaAs epitaxial growth layer 12 by the frost treatment, the light generated by the unevenness 13 is irregularly reflected and spherically dispersed. Therefore, the uniformity of light emitted from the N-type AlGaAs epitaxial growth layer 12 can be improved. Further, since the upper transparent electrode 16 is provided on the entire surface of the N-type AlGaAs epitaxial growth layer 12,
The uniformity of internal light emission near the N junction can be improved. Further, a PEP step was required to form a conventional electrode, but since the upper transparent electrode 16 is provided on the entire surface of the N-type AlGaAs epitaxial growth layer 12, the present invention becomes unnecessary and the manufacturing cost can be reduced.

In the above embodiment, the N-type AlGaAs
On the s epitaxial growth layer, an impurity-doped In
_{Although the 2} O ₃ layer was directly provided, an In ₂ O ₃ layer having a thickness of several hundred angstroms without adding impurities was deposited first.
A thickness of 50 with Sn at a concentration of 5% added on the n ₂ O ₃ layer
An upper transparent electrode having a transmittance of 50% or more with respect to the emission wavelength is formed by depositing an In ₂ O ₃ layer of about 00 angstroms and then performing sintering at a temperature of 400 ° C. for 30 minutes. You may.

The same effect as in the above embodiment can be obtained by such a manufacturing method. In addition, by depositing an In ₂ O ₃ layer having a thickness of several hundred angstroms to which no impurity is added, N-type AlGaAs can be obtained. The surface impurity concentration of the epitaxial growth layer can be made lower than that of the above embodiment.

In order to further improve the light quantity and the brightness of the infrared light emitting device manufactured by the above embodiment, a step of depositing Al (aluminum) on the lower transparent electrode surface or providing a mirror around the pellet. It is good to add a process. When Al is deposited, light emitted from the PN junction is reflected by the Al, and the amount of light at the upper transparent electrode increases. When the mirror is provided, light emitted to the side surface of the infrared light emitting element is reflected by the mirror, and the luminance of the infrared light emitting element is improved. The effect of the above additional step becomes significant when the upper transparent electrode has a transmittance of 50% with respect to the emission wavelength.

FIG. 4 shows the effect of the above embodiment of the present invention, in which AlGaAs / GaAs having a transparent electrode formed entirely and partially on an epitaxial layer.
FIG. 3 shows the relationship between the transmittance of a transparent electrode and the luminous efficiency in a system infrared light emitting device. The term "partial formation" means that the area of the transparent electrode is 50% of that of the epitaxial layer. As shown in FIG. 4, when a transparent electrode having a transmittance of 50% with respect to the emission wavelength is used, even when the transparent electrode is partially formed, the same luminous efficiency as a light emitting element using a conventional electrode can be obtained. When it is formed, the luminous efficiency is improved by 200% as compared with the case where it is partially formed.

FIG. 5 shows a SIMS (Secondary Ion Mass S
This shows the relationship between impurity concentration and depth by spectroscopy) analysis. In the manufacturing process of an AlGaAs / GaAs infrared light emitting device, several hundred angstroms of In ₂ having a thickness of several hundred angstroms to which no impurity is added is formed on the epitaxial layer.
O ₃ layer is deposited. 5% concentration on this In ₂ O ₃ layer
In addition, an In ₂ O ₃ layer having a thickness of about 5000 Å to which Sn is added is deposited. Thereafter, the light-emitting element was sintered at a temperature of 600 ° C. for 30 minutes and a temperature of 40 ° C.
Light-emitting elements which have been sintered at 0 ° C. for 30 minutes are referred to as present invention I and present invention II, respectively. An LED using an electrode formed of AuGe is a conventional example. Simultaneous SIMS analysis of the present inventions I and II and the conventional example were conducted to examine the relationship between the surface concentration of impurities in the epitaxial layer and the depth thereof. As a result, it can be seen that the surface concentration of impurities differs depending on the conditions for forming the conventional electrode and the transparent electrode of the present invention. The impurity concentrations of the present inventions I and II are lower than those of the conventional example. In particular, in the present invention II, the impurity concentration is 1 × 10 ¹⁹ atoms / cm ^{3 in a} shallow portion. It is as follows.

FIG. 6 shows the relationship between the surface impurity concentration of the epitaxial layer and the luminous efficiency. Than this,
Surface impurity concentration is 1 × 10 ¹⁹ atoms / cm ³ It can be seen that the luminous efficiency decreases when the above is reached. This decrease in luminous efficiency is because light is absorbed by the high-concentration diffusion layer generated from surface impurities of the epitaxial layer.

As described above, the AlGaAs / GaAs infrared light emitting device has a transparent electrode having a transmittance of 50% or more with respect to the emission wavelength formed on the entire surface, and the surface impurity concentration of the epitaxial layer is 1 × 10 ¹⁹ atoms / cm ^3. Below,
The As substrate has an impurity concentration of 1 × 10 ¹⁹ atoms / cm ³ on the surface in contact with the P-type AlGaAs epitaxial growth layer.
When the following is set, the luminous efficiency is greatly improved. Therefore, it is clear that light absorption by the high concentration diffusion layer can be avoided and the luminous efficiency is improved by the conditions for forming the transparent electrode of the present invention. The present invention is not limited to the above embodiment, and the following modifications are possible.

The upper transparent electrode is doped with Sn at a concentration of 3%.
The upper transparent electrode is made of N-type AlGaAs.
Doping for forming an ohmic junction with the epitaxial growth layer
Various changes can be made as long as the doping material is used, and the doping concentration of 3% may be changed depending on the doping material. The same can be applied to the lower transparent electrode. Although the upper transparent electrode is made of In ₂ O ₃ , it may be made of a polymer material such as Sn ₂ O-type oxide or polythiazyl.

Further, a P-type GaAs substrate and P-type and N-type AlGaAs are formed on the substrate and the epitaxial growth layer.
Although the infrared light emitting device is configured using the epitaxial growth layer, the following combinations may be used.

By sequentially forming an N-type and a P-type GaAs epitaxial growth layer on the N-type GaAs substrate by the LPE method (liquid phase epitaxial growth method), an infrared light emitting device having an emission wavelength of about 940 nm can be formed.

By sequentially forming an N-type and a P-type GaAsP epitaxial growth layer on an N-type GaAs substrate by a VPE method (vapor phase epitaxial growth method), a red light-emitting element having an emission wavelength of about 650 nm can be formed.

An NPE is formed on an N-type GaP substrate by the LPE method.
By sequentially forming the p-type and p-type GaP epitaxial growth layers, a red to green light emitting device having an emission wavelength of 700 nm to 555 nm can be formed. N-type and P-type GaP
A layer in which Zn and O are doped in the epitaxial growth layer constitutes a red light emitting element, a layer in which N is doped is a yellow to green light emitting element, and a layer in which Te is doped constitutes a green light emitting element. I do.

An N-type GaP substrate is coated with N by a VPE method.
By sequentially forming the p-type and p-type GaAsP epitaxial growth layers, an orange to yellow light emitting device having an emission wavelength of 630 nm to 590 nm can be formed. The emission wavelength differs depending on the composition ratio of As.

On an N-type GaAs substrate, NPE is formed by the LPE method.
-Type, P-type InGaAlP epitaxial growth layer and P
By sequentially forming the type GaAlAs epitaxial growth layers, a green to orange light emitting device having a light emission wavelength of 560 nm to 620 nm can be formed. The emission wavelength varies depending on the Al composition ratio.

An NPE is formed on an N-type SiC substrate by the LPE method.
A blue light emitting device having a light emission wavelength of about 470 nm can be formed by sequentially forming the p-type and p-type SiC epitaxial growth layers.

An NPE is formed on an N-type ZnSe substrate by the LPE method.
By sequentially forming the p-type and p-type ZnSe epitaxial growth layers, a blue light emitting device having an emission wavelength of about 480 nm can be formed. In each of the above structures, the upper and lower transparent electrodes are the same as in the above-described embodiment.

[0031]

As described above, according to the present invention,
A first transparent electrode of an oxide or a polymer material having a transmittance of 50% or more with respect to an emission wavelength is provided on the entire surface of the second epitaxial growth layer of the second conductivity type having irregularities on the surface; 50% of the emission wavelength on the back of the substrate
A second transparent electrode made of an oxide having the above transmittance is provided. The second epitaxial growth layer has an impurity concentration of 1 × 10 ¹⁹ atoms / cm on the surface in contact with the first transparent electrode.
³ or less, and the compound semiconductor substrate has an impurity concentration of 1 × 10 ¹⁹ ato on the surface in contact with the first epitaxial growth layer.
ms / cm ³ or less. Therefore, the uniformity of the internal light emission near the junction between the first epitaxial growth layer and the second epitaxial growth layer is improved, and the emitted light is not absorbed by the impurities of the first transparent electrode and the second epitaxial growth layer. Luminous efficiency and luminance can be improved.

[Brief description of the drawings]

FIG. 1A is a plan view showing a conventional compound semiconductor light emitting device, and FIG. 1B is a side view thereof.

2 (a) to 2 (f) are cross-sectional views showing steps of manufacturing an AlGaAs / GaAs infrared light emitting device according to an embodiment of the present invention.

FIG. 3 (a) is an illustration of an Al according to an embodiment of the present invention.
FIG. 3B is a plan view showing a GaAs / GaAs infrared light emitting device, and FIG.

FIG. 4 is a diagram showing the relationship between the transmittance of a transparent electrode and the luminous efficiency.

FIG. 5 is a diagram showing a relationship between impurity concentration and depth by SIMS analysis.

FIG. 6 is a diagram showing a relationship between a surface impurity concentration of an epitaxial layer and luminous efficiency.

[Explanation of symbols]

10: P-type GaAs substrate, 11: P-type AlGaAs epitaxial growth layer, 12: N-type AlGaAs epitaxial growth layer, 13: unevenness, 15: In ₂ O ₃ layer, 16: upper transparent electrode, 17: In ₂ O ₃ layer, 18 ... lower transparent electrode, 19 ... light emitting element, 20 ... pellet, 21 ... conductive wire, 24 ... electrode terminal,
25 ... conductive stem, 29 ... mold resin

Claims (3)

(57) [Claims] 1. A first conductive type first epitaxial growth layer provided on a compound semiconductor substrate by epitaxial growth, and a second conductive type first conductive growth layer provided on the first epitaxial growth layer and having irregularities on its surface. A second epitaxially grown layer, and an oxide provided on the entire surface of the second epitaxially grown layer and having a transmittance of 50% or more with respect to an emission wavelength .
Or a first transparent electrode of a polymer material, and an emission wavelength provided under the compound semiconductor substrate.
A second transparent electrode made of an oxide having a transmittance of 50% or more. The second epitaxial growth layer has an impurity concentration of 1 × 10 ¹⁹ atoms / surface on the surface in contact with the first transparent electrode. c
m ³ or less, and the compound semiconductor substrate has an impurity concentration of 1 on the surface in contact with the first epitaxial growth layer.
Compound semiconductor light-emitting device characterized by × is 10 ¹⁹ atoms / cm ³ or less. 2. The first transparent electrode includes an In ₂ O ₃ layer,
_2. The compound semiconductor light emitting device according to claim 1, wherein the compound semiconductor light emitting device is made of one of a Sn ₂ O type oxide and a polymer material such as polythiazyl (SN) _x . 3. The semiconductor device according to claim 1, wherein the semiconductor substrate is P-type,
2. The compound semiconductor light emitting device according to claim 1, wherein the epitaxially grown layer is P-type and the second epitaxially grown layer is N-type.