JP3661871B2 - Method for producing gallium nitride compound semiconductor - Google Patents

Description

  The present invention relates to a method for manufacturing an N-type gallium nitride compound semiconductor with controlled electron concentration and conductivity.

JP 62-119196 A JP 63-188977 A

  Conventionally, GaN-based compound semiconductors have been used for blue light-emitting diodes. The GaN-based compound semiconductors are attracting attention because of their direct transition, high luminous efficiency, and the fact that one of the three primary colors of light is blue.

  In such a light emitting diode using a GaN-based compound semiconductor, an N layer made of an N-type GaN-based compound semiconductor is grown on a sapphire substrate directly or with a buffer layer made of aluminum nitride interposed therebetween. The structure is such that an I layer made of an I-type GaN-based compound semiconductor is grown by adding a P-type impurity on the layer (JP-A 62-119196, JP-A 63-188977). )

  When 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. Conversely, unlike semiconductors such as silicon, I In order to obtain an (insulator) type semiconductor, zinc was doped. In addition, when obtaining N-type GaN, it is difficult to control the conductivity.

  However, in the process of manufacturing the above GaN light emitting diode, the present inventor has established a vapor growth technique for a GaN semiconductor by a metal organic compound vapor deposition method, and obtains a high purity GaN vapor deposition film. I was able to. As a result, low-resistivity N-type GaN has been obtained in the past when no impurity doping is performed. However, the present inventors have established a vapor-phase growth technique and have achieved high-resistivity GaN without doping impurities. was gotten.

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

  The invention according to claim 1 is a method of manufacturing a gallium nitride compound semiconductor (GaN), wherein a buffer layer is formed on a substrate at a temperature lower than a growth temperature of the gallium nitride compound semiconductor (GaN), In the process of vapor phase growth using the formed substrate by flowing a gas containing silicon simultaneously with other source gases in a state where the resistivity is high when silicon is not added by the metal organic chemical vapor deposition method. A vapor growth film of N-type gallium nitride compound semiconductor (GaN) whose conductivity is controlled by adding silicon as a donor by controlling the mixing ratio of the gas containing silicon and the other source gas It is a method for producing a gallium nitride compound semiconductor characterized in that it is obtained.

According to the first aspect of the present invention, a buffer layer is formed on a substrate at a temperature lower than the growth temperature of the gallium nitride compound semiconductor (GaN), and an organic metal compound vapor phase growth is performed using the substrate on which the buffer layer is formed. In the process of vapor phase growth by flowing a gas containing silicon simultaneously with other source gases in a state where the resistivity is high when silicon is not added by the method, the mixing ratio of the gas containing silicon and the other source gases By controlling the above, silicon is added as a donor to obtain an N-type gallium nitride compound semiconductor (GaN) vapor-grown film with controlled conductivity.
Thereby, the electrical conductivity is controlled, and a gallium nitride semiconductor having an electrical conductivity accurately having a desired value can be obtained. As a result, it is possible to obtain a high carrier concentration layer and a low carrier concentration layer that are formed in a state where the conductivity (1 / resistivity) can be controlled. A light-emitting element with improved strength can be obtained.

Hereinafter, the present invention will be described based on specific examples.
The light emitting diode 10 having the structure shown in FIG. 1 was manufactured using the manufacturing method of the present invention.

In FIG. 1, a light emitting diode 10 has a sapphire substrate 1, and a 500 Al AlN buffer layer 2 is formed on the sapphire substrate 1. On the buffer layer 2, a high carrier concentration N ⁺ layer 3 made of GaN having a thickness of about 2.2 μm and a low carrier concentration N layer 4 made of GaN having 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. An electrode 7 made of aluminum connected to the I layer 5 and an electrode 8 made of aluminum connected to the high carrier concentration N ⁺ layer 3 are formed.

Next, a method for manufacturing the light emitting diode 10 having this structure will be described.
The light emitting diode 10 was manufactured by vapor phase growth using a metal organic compound vapor phase growth method (hereinafter referred to as “M0VPE”). The gases used were NH ₃ , carrier gas H ₂ , 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, the single crystal sapphire substrate 1 having the a-plane as a main surface cleaned by organic cleaning and heat treatment is mounted on a susceptor mounted in the reaction chamber of the M0VPE apparatus. Next, the sapphire substrate 1 was vapor-phase etched at a temperature of 1200 ° C. for 10 minutes while H ₂ was flowed into the reaction chamber at a flow rate of 2 l / min. Next, the temperature was lowered to 400 ° C., H ₂ was supplied at a flow rate of 20 l / min, NH ₃ was supplied at a flow rate of 10 l / min, and H ₂ bubbled with TMA maintained at 15 ° C. was supplied at 50 cc / min. AlN buffer layer 2 was formed to a thickness of about 500 mm.

Next, 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 as another source gas is 10 l / min and -15 ° C. H ₂ with bubbling of retained TMG was flowed at 100 cc / min, and silane (SiH ₄ ) diluted to 0.86 ppm with H ₂ as a gas containing silicon was flowed at 200 ml / min for 30 min to obtain a film thickness of about 2.2 μm. 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 maintained at 1150 ° C., H ₂ is bubbled with 20 l / min, NH ₃ is 10 l / min, and TMG held at −15 ° C. is bubbled with H ₂ at 100 cc / min. By flowing for 20 minutes, a low carrier concentration N layer 4 made of GaN having a thickness of about 1.5 μm and a carrier concentration of 1 × 10 ¹⁵ / cm ³ or less was formed.

Next, the sapphire substrate 1 is set to 900 ° C., H ₂ is 20 l / min, NH ₃ is 10 l / min, TMG is 1.7 × 10 ⁻⁴ mol / min, DEZ is 1.5 × 10 ⁻⁴ mol / min. The I layer 5 made of GaN having a thickness of 0.2 μm was formed by supplying at a ratio. In this way, a multilayer structure as shown in FIG. 2 was obtained.

Next, as shown in FIG. 3, a SiO ₂ layer 11 was formed on the I layer 5 to a thickness of 2000 mm by sputtering. Next, a photoresist 12 was applied on the SiO ₂ layer 11, and the photoresist 12 was formed by photolithography in a pattern in which the photoresist at the electrode formation site with respect to 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 etching solution. Next, as shown in FIG. 5, a part of the upper surface of the I layer 5 at a portion not covered with the photoresist 12 and the SiO ₂ layer 11, the low carrier concentration N layer 4 and the high carrier concentration N ⁺ layer 3 therebelow. The sample was dry-etched by supplying a vacuum degree of 0.04 Torr, a high-frequency power of 0.44 W / cm ² and CCl ₂ F ₂ gas at 10 ml / min, and then dry-etched 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. 7, an Al layer 13 was formed by vapor deposition on the entire upper surface of the sample. Then, a photoresist 14 is applied on the Al layer 13, and a pattern is formed in a predetermined shape so that the photoresist 14 has electrode portions for the high carrier concentration N ⁺ layer 3 and the I layer 5 by photolithography. did. 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 formed. Electrode 8 and electrode 7 of I layer 5 were formed.

In this manner, a gallium nitride-based light emitting device having a MIS (Metal-Insulator-Semiconductor) structure 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 grown, T ₂ is maintained at 20 L / min for H ₂ , 10 l / min for NH ₃ as another source gas, and at −15 ° C. of H ₂ which was bubbled flowed at 100 cc / min, by controlling the silane diluted with H ₂ to 0.86ppm as a gas containing silicon (SiH ₄₎ in the range of 10 cc / min to 300 cc / min, a high carrier The resistivity (= 1 / conductivity) of the concentration N ⁺ layer 3 can be changed from 3 × 10 ⁻¹ Ωcm to 8 × 10 ⁻³ Ωcm as shown in FIG. Similarly, if the above silane (SiH ₄ ) is controlled in the range of 10 cc / min to 300 cc / min, the carrier concentration (electron concentration) of the high carrier concentration N ⁺ layer 3 is 6 as shown in FIG. It can be changed from × 10 ¹⁶ / cm ³ to 3 × 10 ¹⁸ / cm ³ .

In the above method, although silane (SiH ₄ ) is controlled, the flow rate of other source gases may be controlled, and the resistivity may be changed by controlling the mixing ratio of the two. In this embodiment, silane is used as the Si dopant material, but a gas obtained by bubbling an organic compound containing Si such as tetraethylsilane (Si (C ₂ H ₅ ) ₄ ) with H ₂ may be used. In this manner, the high carrier concentration N ⁺ layer 3 and the low carrier concentration N layer 4 could be formed in a state where the resistivity can be controlled.

  As a result, the light emission 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 composed of the I layer and the N layer. Further, when the light emitting surface was observed, it was also observed that the number of light emitting points was increased.

  The present invention is used in a method for manufacturing an N-type gallium nitride compound semiconductor with controlled electron concentration and conductivity. In particular, it is effective for a method for manufacturing a light-emitting element using an N-type gallium nitride compound semiconductor whose electron concentration and conductivity are controlled. The present invention is also effective in improving the light emission efficiency of a blue light emitting gallium nitride compound semiconductor light emitting device.

The block diagram which showed the structure of the light emitting diode which concerns on one specific Example of this invention. Sectional drawing which showed the manufacturing process of the light emitting diode of the Example Sectional drawing which showed the manufacturing process of the light emitting diode of the Example Sectional drawing which showed the manufacturing process of the light emitting diode of the Example Sectional drawing which showed the manufacturing process of the light emitting diode of the Example Sectional drawing which showed the manufacturing process of the light emitting diode of the Example Sectional drawing which showed the manufacturing process of the light emitting diode of the Example The measurement figure which showed the relationship between the flow volume of silane gas, and the electrical property of the N layer by which vapor phase growth was carried out.

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

Claims (1)

  A method for producing a gallium nitride compound semiconductor (GaN), comprising: forming a buffer layer on a substrate at a temperature lower than a growth temperature of the gallium nitride compound semiconductor (GaN); and using the substrate on which the buffer layer is formed, In the process of vapor phase growth by flowing a gas containing silicon simultaneously with another source gas in a state where the resistivity is high when silicon is not added by metal compound vapor deposition, the gas containing silicon and the other Nitride gallium nitride compound semiconductor (GaN) vapor-deposited film having controlled conductivity by adding silicon as a donor by controlling the mixing ratio with the source gas of gallium nitride Semiconductor manufacturing method.

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