JPH10261817A - Gallium nitride compound semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the luminous efficacy of a semiconductor light emitting element by using an N-type GaN compound semiconductor in which the carrier concentration is controlled. SOLUTION: After an AlN buffer layer 2 having a thickness of 500Åis formed on a sapphire substrate 1, a silicon-doped N<+> -GaN layer having a film thickness of about 2.2 μm, an electron concentration of 1.5×10<18> /cm<3> , and a high carrier concentration, an N-GaN layer 4 having a film thickness of about 1.5 μm, an electron concentration of <=1×10<15> /cm<3> , and a low carrier concentration, and an I-GaN layer 5 having a film thickness of about 0.2 μm are successively formed on the buffer layer 2. On the I- and N<+> -GaN layers 5 and 3, aluminum electrodes 7 and 8 which are connected to each other are formed, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride based compound semiconductor light emitting device which emits blue light with improved luminous efficiency.

[0002]

2. Description of the Related Art Heretofore, GaN-based compound semiconductors have been used for blue light emitting diodes. The GaN-based compound semiconductor has attracted attention because of its direct transition, high luminous efficiency, and the use of blue, one of the three primary colors of light, as the luminescent color.

A light-emitting diode using such a GaN-based compound semiconductor is an N-type Ga-type semiconductor device directly on a sapphire substrate or with a buffer layer of aluminum nitride interposed therebetween.
It has a structure in which an N layer made of an N-based compound semiconductor is grown, and a layer made of a GaN-based compound semiconductor doped with a P-type impurity is grown on the N-layer (Japanese Patent Laid-Open No. 62-11919).
No. 6, JP-A-63-188977).

[0004]

When a light emitting diode having the above structure is manufactured, a junction between a P-type doped layer and an N layer is used. When a GaN-based compound semiconductor is manufactured, usually, the GaN-based compound semiconductor exhibits an N conductivity type without intentionally doping impurities. Also, when obtaining N-type GaN, it was difficult to control its conductivity.

However, in the process of manufacturing the above-mentioned GaN light emitting diode, the present inventor has established a technique for vapor-phase growth of a GaN semiconductor by a metalorganic compound vapor-phase epitaxy method, and has produced a high-purity GaN vapor-phase grown film. I got it. As a result, conventionally, when doping of impurities is not performed,
Although low resistivity N-type GaN was obtained, high resistivity GaN was obtained without doping with impurities due to the establishment of the vapor growth technique of the present inventors.

On the other hand, in the future, in order to improve the characteristics of the GaN light emitting diode, it has become necessary to intentionally obtain a GaN-based compound semiconductor vapor grown film whose conductivity can be controlled. Therefore, an object of the present invention is to improve the luminous efficiency of a light emitting device having a GaN-based compound semiconductor layer by controlling the resistivity by silicon doping in the light emitting device.

[0007]

According to the first aspect of the present invention, there is provided a sapphire substrate, and a carrier concentration of 6 is formed on the sapphire substrate by a metalorganic compound vapor deposition method and silicon is added at a predetermined concentration. × 10 ^{16 to} 3 × 1
A gallium nitride-based compound semiconductor light-emitting device having an n-type gallium nitride-based compound semiconductor layer set to a desired value in the range of 0 ¹⁸ / cm ³ .

According to a second aspect of the present invention, the n-type gallium nitride-based compound semiconductor layer is made of Al _X Ga _{1 -X} N (including X = 0). The n-type gallium nitride compound semiconductor layer is GaN.

According to a fourth aspect of the present invention, a buffer layer is formed on a sapphire substrate, and an n-type gallium nitride-based compound semiconductor layer is formed on the buffer layer. The invention is characterized in that the buffer layer is formed on the sapphire substrate at a temperature lower than the growth temperature of the n-type gallium nitride-based compound semiconductor layer by an organometallic compound vapor deposition method. The buffer layer is grown at a temperature of about 400.degree.

According to a seventh aspect of the present invention, there are provided two electrodes formed on the same surface side, one of which is formed on an n-type gallium nitride-based compound semiconductor layer. .

[0011]

According to the first aspect of the present invention, a carrier concentration of 6 × 10 ¹⁶ is formed on a sapphire substrate by an organometallic compound vapor deposition method and silicon is added at a predetermined concentration. Since the desired value is in the range of 3 × 10 ¹⁸ / cm ³ , in a high-quality crystal, the amount of silicon added is controlled, a desired carrier concentration can be obtained, and the crystallinity of a layer contributing to light emission is improved. Since the carrier injection efficiency is improved, the luminous efficiency is improved.

According to the second and third aspects of the present invention, the n-type gallium nitride-based compound semiconductor layer is made of Al _x Ga _{1 -x}
By using N (including X = 0) and GaN, a layer having a large band gap and a high carrier concentration can be obtained, so that the function of the n-type cladding layer and the n-type contact layer can be improved. .

According to a fourth aspect of the present invention, a buffer layer is formed on a sapphire substrate. In the fifth aspect of the present invention, the buffer layer is formed at a temperature lower than the growth temperature of the n-type gallium nitride-based compound semiconductor layer. In the invention according to claim 6, the buffer layer is grown at a temperature of about 400 ° C., so that the layer on the buffer layer is high when silicon is not added. The crystallinity can be improved so as to provide resistance, and the controllability of the carrier concentration when adding a syringe is improved.

According to the seventh aspect of the present invention, since an n-type layer having a low resistivity can be obtained, a voltage drop in the n-type layer can be reduced even if two electrodes are formed on the same surface side. .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific embodiments. The light emitting diode 10 having the structure shown in FIG. 1 was manufactured by using the manufacturing method of the present invention.

In FIG. 1, a light emitting diode 10 has a sapphire substrate 1 and 50
An AlN buffer layer 2 of 0 ° is formed. On the buffer layer 2, a high carrier concentration N ⁺ layer 3 made of GaN with a thickness of about 2.2 μm and a low carrier concentration N layer 4 made of GaN with a thickness of about 1.5 μm are formed in this order. Further, an I layer 5 made of GaN having a thickness of about 0.2 μm is formed on the low carrier concentration N layer 4. Then, an electrode 7 made of aluminum connected to the I layer 5 and a high carrier concentration N ⁺
An electrode 8 made of aluminum connected to the layer 3 is formed.

Next, a method of manufacturing the light emitting diode 10 having this structure will be described. The light emitting diode 10 includes:
It was manufactured by vapor phase growth by metal organic compound vapor phase epitaxy (hereinafter referred to as "M0VPE").

The gases used were NH ₃ and carrier gas H ₂
Trimethyl gallium _{(Ga (CH 3) 3)} ( hereinafter referred to as "TMG") and trimethylaluminum _{(Al (CH 3) 3)} ( hereinafter "TMA
), Silane (SiH ₄ ) and diethylzinc (hereinafter “DEZ
").

First, a single-crystal sapphire substrate 1 whose main surface is the a-plane cleaned by organic cleaning and heat treatment is mounted on a susceptor placed in a reaction chamber of an MOVPE apparatus. Then H ₂
Was flowed into the reaction chamber at a flow rate of 2 l / min, and the sapphire substrate 1 was subjected to gas phase etching at 1200 ° C. for 10 minutes.

Next, the temperature was lowered to 400 ° C., and H ₂ was maintained at a flow rate of 20 l / min, NH ₃ was maintained at a flow rate of 10 l / min, and TM was maintained at 15 ° C.
Buffer layer 2 of AlN was formed to a thickness of about 500Å and H ₂ which was bubbled A was supplied at 50 cc / min.

Next, the supply of TMA is stopped, the temperature of the sapphire substrate 1 is maintained at 1150 ° C., H ₂ is 20 l / min, NH ₃ is 10 l / min as another source gas, and of H ₂ which was bubbled TMG kept at 15 ℃ flowed at 100 cc / min, silane diluted with H ₂ to 0.86ppm as a gas containing silicon (SiH ₄₎ and 30 shunted 200ml / min, thickness About 2.2μm,
To form a high carrier concentration N ⁺ layer 3 made of GaN having a carrier concentration 1.5 × 10 ¹⁸ / cm ^3.

Subsequently, the temperature of the sapphire substrate 1 is set to 1150 ° C.
Held in the H ₂ 20 l / min, the NH ₃ 10 l / min, -15 ° C.
Of H ₂ which was bubbled TMG held at 100 cc / min to 20
Flow for about 1.5 minutes, thickness about 1.5μm, carrier concentration 1 × 10 ¹⁵ / c
A low carrier concentration N layer 4 made of GaN of m ³ or less was formed.

Next, the sapphire substrate 1 is heated to 900 ° C.
H ₂ was supplied at a rate of 20 l / min, NH ₃ was supplied at a rate of 10 l / min, TMG was supplied at a rate of 1.7 × 10 ⁻⁴ mol / min, and DEZ was supplied at a rate of 1.5 × 10 ⁻⁴ mol / min.
An I layer 5 made of GaN having a thickness of 0.2 μm was formed. Thus, a multilayer structure as shown in FIG. 2 was obtained. Next, as shown in FIG. 3, an SiO ₂ layer 11 was formed to a thickness of 2000 ° on the I layer 5 by sputtering. Next, a photoresist 12 was applied on the SiO ₂ layer 11, and the photoresist 12 was formed by photolithography into a pattern in which the photoresist at the electrode formation site for the high carrier concentration N ⁺ layer 3 was removed.

Next, as shown in FIG. 4, the SiO ₂ layer 11 not covered with the photoresist 12 was removed with a hydrofluoric acid-based etchant. Next, as shown in FIG. 5, a part of the upper surface of the I layer 5 which is not covered by the photoresist 12 and the SiO ₂ layer 11, and the low carrier concentration N layer 4 and the high carrier concentration N ⁺ layer 3 thereunder. Was dry-etched by supplying a CCl ₂ F ₂ gas at a vacuum degree of 0.04 Torr, high-frequency power of 0.44 W / cm ² and CCl ₂ F ₂ gas at 10 ml / min, and then dry-etching with Ar. next,
As shown in FIG. 6, the SiO ₂ layer 11 remaining on the I layer 5 was removed with hydrofluoric acid.

Next, as shown in FIG.
The Al layer 13 was formed by vapor deposition. And the Al layer 13
Is coated on the photoresist 14 and the photoresist 14 has a high carrier concentration N by photolithography.
^A pattern was formed in a predetermined shape so that the electrode portions for the ⁺ layer 3 and the I layer 5 remained. Next, as shown in FIG. 7, the exposed portion of the lower Al layer 13 is etched with a nitric acid-based etchant using the photoresist 14 as a mask, the photoresist 14 is removed with acetone, and the high carrier concentration N ⁺ layer 3 is removed. The electrode 8 and the electrode 7 of the I layer 5 were formed.

Thus, a gallium nitride-based light emitting device having the structure shown in FIG. 1 can be manufactured. In the above manufacturing process, when the high carrier concentration N ⁺ layer 3 is vapor-phase grown, H ₂ is 20 l / min and NH ₃ as another source gas is 10 l / min.
/ Min and H ₂ bubbled with TMG maintained at -15 ° C
The flowed at 100 cc / min, 0.86 with H ₂ as a gas containing silicon
By controlling silane (SiH ₄ ) diluted to ppm in the range of 10 cc / min to 300 cc / min, a high carrier concentration N ⁺ layer 3
As shown in FIG. 8, the resistivity of 3 × 10 ⁻¹ Ωcm to 8 × 1
It can be changed to 0 ^-3 Ωcm. Similarly, the carrier concentration of the high carrier concentration N ⁺ layer 3 can be changed from 6 × 10 ¹⁶ to 3 × 10 ¹⁸ / cm ³ as shown in FIG.

In the above method, silane (SiH ₄ ) is controlled. However, the flow rate of another source gas may be controlled, or the mixing ratio of the two may be controlled to change the resistivity. In this example, silane was used as the Si dopant material, but an organic compound containing Si, for example, tetraethylsilane
A gas in which (Si (C ₂ H ₅ ) ₄ ) or the like is bubbled with H ₂ may be used. Thus, the high carrier concentration N ⁺ layer 3 and the low carrier concentration N layer 4 were formed in a state where the resistivity was controllable.

As a result, the light emitting intensity of the light emitting diode 10 manufactured by the above method was 0.2 mcd, which was four times higher than that of the conventional light emitting diode having the I layer and the N layer. When the light emitting surface was observed, it was also observed that the number of light emitting points increased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a light emitting diode according to a specific embodiment of the present invention.

FIG. 2 is a sectional view showing a manufacturing process of the light emitting diode of the embodiment.

FIG. 3 is a sectional view showing a manufacturing process of the light-emitting diode of the embodiment.

FIG. 4 is a sectional view showing a manufacturing process of the light emitting diode of the embodiment.

FIG. 5 is a sectional view showing a manufacturing process of the light-emitting diode of the embodiment.

FIG. 6 is a sectional view showing a manufacturing process of the light-emitting diode of the example.

FIG. 7 is a sectional view showing a manufacturing process of the light emitting diode of the embodiment.

FIG. 8 is a measurement diagram showing the relationship between the flow rate of a silane gas and the electrical characteristics of a vapor-grown N layer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Light emitting diode 1 ... Sapphire substrate 2 ... Buffer layer 3 ... High carrier concentration N ⁺ layer 4 ... Low carrier concentration N layer 5 ... I layer 7, 8 ... Electrode

 ──────────────────────────────────────────────────続 き Continuing from the front page (71) Applicant 396020800 Japan Science and Technology Agency 4-1-8, Honcho, Kawaguchi-shi, Saitama (72) Inventor Michinari Saga 1 Ochiai-Ochiai, Kasuga-cho, Nishikasugai-gun, Aichi Prefecture Toyoda Gosei Inside (72) Inventor Katsuhide Shinbe 1 Ochiai Nagahata, Kasuga-cho, Nishi-Kasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. In-house (72) Kuki Kato, Inventor 1 at Nagata, Ochiai, Kasuga-cho, Nishi-Kasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. ) Inventor Isamu Akasaki Naoichi-shi, Aichi

Claims (7)

[Claims] 1. A sapphire substrate, and a carrier concentration of 6.times.1 is formed on the sapphire substrate by a metalorganic compound vapor deposition method and silicon is added at a predetermined concentration.
A gallium nitride-based compound semiconductor light emitting device having an n-type gallium nitride-based compound semiconductor layer set to a desired value in the range of 0 ^{16 to} 3 × 10 ¹⁸ / cm ³ . 2. The method according to claim 1, wherein the n-type gallium nitride-based compound semiconductor layer is
The gallium nitride-based compound semiconductor light emitting device according to claim 1, comprising Al _X Ga _1-X N (including X = 0). 3. The n-type gallium nitride-based compound semiconductor is Ga
The gallium nitride-based compound semiconductor light-emitting device according to claim 1, comprising N 2. 4. The semiconductor device according to claim 1, wherein a buffer layer is formed on said sapphire substrate, and said n-type gallium nitride-based compound semiconductor layer is formed on said buffer layer. 12. The gallium nitride-based compound semiconductor light-emitting device according to item 10. 5. The method according to claim 4, wherein the buffer layer is formed on a sapphire substrate at a temperature lower than a growth temperature of the n-type gallium nitride-based compound semiconductor layer by a metal organic compound vapor deposition method. The gallium nitride-based compound semiconductor light-emitting device according to the above. 6. The gallium nitride based compound semiconductor light emitting device according to claim 5, wherein said buffer layer is grown at a temperature of about 400 ° C. 7. It has two electrodes formed on the same surface side,
The gallium nitride-based compound semiconductor light emitting device according to any one of claims 1 to 6, wherein one of the electrodes is formed on the n-type gallium nitride-based compound semiconductor layer.