JP2002100807A - Method for manufacturing gallium nitride based compound semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve luminous efficiency of a light-emitting element by obtaining N-type GaN-based compound semiconductor, whose electron concentration is controlled. SOLUTION: A buffer layer 2 of AlN of 500 Å is formed on a sapphire substrate 1. A silicon-doped high carrier concentration N+ layer 3 of GaN, whose film thickness is about 2.2 μm and electron concentration is 1.5×1018/cm3, a low carrier concentration N layer 4 of GaN whose film thickness is about 1.5 μm and electron concentration is at most 1×1015/cm3, and an I layer 5 whose film thickness is about 0.2 μm and which is composed of GaN are formed, in the order on the buffer layer 2. In the I layer 5 and the high carrier concentration N+ layer 3, electrodes 7, 8, which are in contact with the I layer 5 and the N+ layer 3, respectively and formed of aluminum, are formed. Resistivity (=1/conductivity) of the N+ layer 3 can be made to change from 3×10-1 Ωcm to 8×10-3 Ωcm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an N-type gallium nitride compound semiconductor having a controlled electron concentration and conductivity, and more particularly to a method of manufacturing an N-type gallium nitride based semiconductor having a controlled electron concentration and conductivity. The present invention relates to a method for manufacturing a light emitting device using a compound semiconductor. Further, the present invention is effective for improving the luminous efficiency of a gallium nitride-based compound semiconductor light emitting device that emits blue light.

[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.
An N-layer composed of an N-type compound semiconductor is grown, and a P-type impurity is added on the N-layer to grow an I-layer composed of an I-type GaN-based compound semiconductor. Akira
62-119196, JP-A-63-188977).

[0004]

In manufacturing a light emitting diode having the above structure, a junction between an I layer and an N layer is used. When a GaN-based compound semiconductor is manufactured, the GaN-based compound semiconductor is usually of N conductivity type without intentionally doping impurities. To obtain an (Insulator) type semiconductor, zinc was doped. 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 of vapor-phase growth of a GaN semiconductor by a metalorganic compound vapor-phase epitaxy method, and has developed a high-purity GaN vapor-phase growth film. Could be obtained.
As a result, conventionally, low-resistivity N-type GaN was obtained without doping with impurities. However, with the establishment of the vapor growth technique of the present inventors, high-resistivity GaN without doping with impurities was obtained. was gotten.

On the other hand, in order to improve the characteristics of the above-mentioned GaN light emitting diode, it is necessary to obtain an N-type GaN-based compound semiconductor vapor deposition film whose conductivity can be intentionally controlled. . Accordingly, an object of the present invention is to establish a technique for manufacturing an N-type GaN-based compound semiconductor in which the resistivity (1 / conductivity) and the electron concentration can be controlled.

[0007]

According to a first aspect of the present invention, there is provided a method of manufacturing a gallium nitride-based compound semiconductor light emitting device, wherein a buffer layer is formed on a sapphire substrate by an organic metal compound vapor deposition method, and the buffer layer is formed. Using a sapphire substrate on which a layer is formed, flowing a gas containing silicon at the same time as another source gas by an organic metal compound vapor phase epitaxy method, and controlling a mixing ratio of the gas containing silicon and the other source gas. Forming a high carrier concentration layer made of an n-type gallium nitride semiconductor with controlled conductivity within a range where the conductivity (1 / resistivity) monotonically increases with an increase in silicon concentration; Forming a low carrier concentration layer made of a gallium nitride semiconductor. According to a second aspect of the present invention, in the method for manufacturing a gallium nitride-based compound semiconductor light emitting device, a buffer layer is formed on a sapphire substrate by a metalorganic compound vapor deposition method, and the sapphire substrate on which the buffer layer is formed is used. Then, by the metalorganic compound vapor deposition method, a gas containing silicon is caused to flow at the same time as another source gas, and the mixture ratio of the gas containing silicon and the other source gas is controlled, whereby the carrier concentration with respect to the silicon concentration is increased. Forming a high carrier concentration layer made of an n-type gallium nitride semiconductor with controlled conductivity within a range where monotonically increases;
Forming a low carrier concentration layer made of a GaN-type gallium nitride semiconductor.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the high carrier concentration layer is a state in which gallium nitride has a high resistivity when grown without adding silicon. By flowing a gas containing silicon at the same time as another source gas, and controlling the mixing ratio of the gas containing silicon and the other source gas, forming a layer made of gallium nitride with controlled conductivity. Features.
According to a fourth aspect of the present invention, in the third aspect of the invention, the state in which gallium nitride has a high resistivity is 1 × 10 ¹⁵ / cm ³ or less in terms of electron concentration. . According to a fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the sapphire substrate is subjected to gas phase etching with hydrogen gas before forming the buffer layer. And The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the buffer layer is made of aluminum nitride. According to a seventh aspect of the present invention, in the first aspect of the present invention, the buffer layer is formed at a temperature lower than the growth temperature of the layer of gallium nitride having controlled conductivity. It is characterized by being formed.

[0009]

According to the first aspect of the present invention, a buffer layer is formed on a sapphire substrate by an organic metal compound vapor deposition method, and an organic metal compound is formed using the sapphire substrate on which the buffer layer is formed. By the vapor growth method, a gas containing silicon is caused to flow at the same time as another source gas, and by controlling the mixing ratio of the gas containing silicon and the other source gas, the conductivity (1 / resistivity) with respect to the silicon concentration is increased. A) a step of forming a high carrier concentration layer made of an n-type gallium nitride semiconductor having a controlled conductivity and a step of forming a low carrier concentration layer made of an n-type gallium nitride semiconductor within a range where monotonously increases. are doing. Thereby, the conductivity is controlled, and a gallium nitride semiconductor having a desired value of conductivity can be obtained accurately. As a result, a high carrier concentration layer and a low carrier concentration layer formed with controllable electric conductivity (1 / resistivity) can be obtained, so that a light-emitting element with improved emission intensity can be obtained.

According to a second aspect of the present invention, a buffer layer is formed on a sapphire substrate by an organometallic compound vapor deposition method, and the organometallic compound vapor deposition method is performed using the sapphire substrate on which the buffer layer is formed. By flowing a gas containing silicon at the same time as another source gas and controlling the mixing ratio of the gas containing silicon and the other source gas, the conductivity is increased within a range in which the carrier concentration monotonically increases with respect to the silicon concentration. Forming a high carrier concentration layer made of an n-type gallium nitride semiconductor with a controlled rate; and forming a low carrier concentration layer made of an n-type gallium nitride semiconductor. This controls the carrier concentration,
A gallium nitride semiconductor having a desired carrier concentration accurately can be obtained. As a result, a high carrier concentration layer and a low carrier concentration layer formed in a state where the carrier concentration can be controlled can be obtained, so that a light-emitting element with improved emission intensity can be obtained. According to a third aspect of the present invention, in the high carrier concentration layer, in a state where gallium nitride has a high resistivity when grown without adding silicon, a gas containing silicon is caused to flow simultaneously with another source gas, and By controlling the mixing ratio of a gas containing GaN and another source gas, a layer made of gallium nitride with controlled conductivity is formed. Thereby, the controllability of the conductivity of the high carrier concentration layer can be improved. Thus, a light-emitting element with improved emission intensity can be obtained.

According to a fourth aspect of the present invention, the gallium nitride has a high resistivity when the electron concentration is 1 × 10 ¹⁵ / cm 3.
³ or less. Thus, in the vapor phase growth process, the gas containing silicon is caused to flow at the same time as the other source gases, and by controlling the mixing ratio between the gas containing silicon and the other source gases, the electron concentration is reduced to 1 × 10
^{In the} concentration range higher than ¹⁵ / cm ³ , the conductivity can be controlled. Thus, a light-emitting element with improved emission intensity can be obtained. According to the fifth aspect of the present invention, since the sapphire substrate is subjected to gas phase etching with hydrogen gas before forming the buffer layer, the crystallinity of the gallium nitride layer is improved and the controllability of the conductivity is improved. Become. Thus, a light-emitting element with improved emission intensity can be obtained. According to the invention described in claim 6, the buffer layer that improves the crystallinity of gallium nitride can be specifically configured by using aluminum nitride (AlN) for the buffer layer. In the invention according to claim 7, the buffer layer is formed at a temperature lower than the growth temperature of the layer made of gallium nitride with controlled conductivity, so that the crystallinity of gallium nitride can be improved. The controllability of the conductivity can be improved. Thus, a light-emitting element with improved emission intensity can be obtained.

[0012]

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.

Referring to 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 an organometallic compound vapor phase growth method (hereinafter referred to as “M0VPE”). The gas used was NH
₃ and the carrier gas H ₂ and trimethylgallium (Ga (CH _{3) 3)}
(Hereinafter referred to as "TMG") and trimethylaluminum (Al
(CH ₃ ) ₃ ) (hereinafter referred to as “TMA”), silane (SiH ₄ ), and diethylzinc (hereinafter referred to as “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., H ₂ was flowed at 20 l / min, NH ₃ was flowd at 10 l / min, and H ₂ bubbled with TMA held at 15 ° C.
Was supplied at 50 cc / min to form an AlN buffer layer 2 having a thickness of about 500 °.

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 by 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
A photoresist 14 is applied on the
The photoresist 14 has a high carrier concentration N
⁺A predetermined shape such that the electrode portions for the layer 3 and the I layer 5 remain.
A pattern was formed. Next, as shown in FIG.
Exposing lower Al layer 13 using photoresist 14 as a mask
Part is etched with a nitric acid-based etchant,
Are removed with acetone, and a high carrier concentration N ⁺Layer 3
The electrode 8 and the electrode 7 of the I layer 5 were formed.

In this manner, the MIS (Me
tal-Insulator-Semiconductor)
An optical element can be manufactured. In the above manufacturing process
And high carrier concentration N⁺When layer 3 is grown by vapor phase, H_Two
20 l / min, NH as other source gas_ThreeThe 10 l / min
And bubbled TMG held at -15 ° C_TwoThe 100c
Flow at c / min, H as a gas containing silicon_Two0.86 ppm
Silane diluted with (SiH_Four) Range from 10cc / min to 300cc / min
, The high carrier concentration N⁺Layer 3 resistance
The rate (= 1 / conductivity) was 3 × 10, as shown in FIG.^-1Ω
cm to 8 × 10^-3Can be changed to Ωcm. As well
In addition, the above silane (SiH_Four) Range from 10cc / min to 300cc / min
, The high carrier concentration N⁺Layer 3 carrier concentration
(Electron concentration) was 6 × 10¹⁶/cm^ThreeFrom
3 × 10 ¹⁸/cm^ThreeCan be varied up to

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 the light-emitting intensity 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. (72) Inventor Akira Umabuchi 1 Ochiai Nagahata, Kasuga-cho, Nishi-Kasugai-gun, Aichi 1 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. (72) Inventor, Masafumi Hashimoto 41-41, Nagatuku, Yoji, Nagakute-cho, Aichi-gun, Aichi ) Inventor Isamu Akasaki Furo-cho, Chigusa-ku, Nagoya-shi, Aichi (No address) F-term in Nagoya University (reference) 5F041 AA03 CA02 CA40 CA49 CA57 CA64 CA74 CA83 5F045 AA04 AB09 AB14 AC08 AC12 AC19 AD08 AD13 AD15 AF09 CA11 CB10 DA53 DA58 DA60 DA62 EB13 EB15 EE12 HA13 HA14

Claims (7)

[Claims] In a method of manufacturing a gallium nitride based compound semiconductor light emitting device, a buffer layer is formed on a sapphire substrate by a metalorganic compound vapor deposition method, and the sapphire substrate on which the buffer layer is formed is used.
By the organometallic compound vapor deposition method, a gas containing silicon is caused to flow at the same time as the other source gas, and by controlling the mixing ratio of the gas containing silicon and the other source gas, the silicon concentration is increased. Conductivity (1 / resistivity)
Is controlled monotonically within a range where n is monotonically increasing.
A method for manufacturing a gallium nitride-based compound semiconductor light emitting device, comprising: a step of forming a high carrier concentration layer made of a n-type gallium nitride semiconductor; and a step of forming a low carrier concentration layer made of an n-type gallium nitride semiconductor. 2. A method for manufacturing a gallium nitride-based compound semiconductor light emitting device, comprising: forming a buffer layer on a sapphire substrate by a metalorganic compound vapor phase epitaxy method, using the sapphire substrate on which the buffer layer is formed;
By the organometallic compound vapor deposition method, a gas containing silicon is caused to flow at the same time as another source gas, and by controlling the mixing ratio of the gas containing silicon and the other source gas, the carrier concentration is increased with respect to the silicon concentration. Forming a high carrier concentration layer made of an n-type gallium nitride semiconductor with controlled conductivity and a step of forming a low carrier concentration layer made of an n-type gallium nitride semiconductor within a range where monotonically increases. A method for manufacturing a gallium nitride-based compound semiconductor light emitting device, comprising: 3. The high carrier concentration layer contains a silicon-containing gas by flowing a gas containing silicon simultaneously with another source gas in a state where gallium nitride has a high resistivity when grown without adding silicon. The gallium nitride-based compound according to claim 1, wherein a layer made of gallium nitride having controlled conductivity is formed by controlling a mixing ratio of a gas and the other source gas. 4. A method for manufacturing a semiconductor light emitting device. 4. The gallium nitride-based compound semiconductor light emitting device according to claim 3, wherein the state in which the gallium nitride has a high resistivity is an electron concentration of 1 × 10 ¹⁵ / cm ³ or less. Production method. 5. The gallium nitride-based system according to claim 1, wherein the sapphire substrate is subjected to gas phase etching with hydrogen gas before forming the buffer layer. A method for manufacturing a compound semiconductor light emitting device. 6. The method of manufacturing a gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein said buffer layer is made of aluminum nitride. 7. The buffer layer according to claim 1, wherein the buffer layer is formed at a temperature lower than a growth temperature of the gallium nitride layer whose conductivity is controlled. 3. The method for manufacturing a gallium nitride-based compound semiconductor light-emitting device according to 1.