JP4193379B2 - Method for producing group 3-5 compound semiconductor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nitride group 3-5 represented by the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1). The present invention relates to a method for manufacturing a compound semiconductor.
[0002]
[Prior art, problems to be solved by the invention]
As a material of a light emitting element such as an ultraviolet, blue or green light emitting diode or an ultraviolet, blue or green laser diode, the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y A group 3-5 compound semiconductor represented by ≦ 1, 0 ≦ z ≦ 1) is known. Hereinafter, x, y, and z in this general formula may be referred to as InN mixed crystal ratio, GaN mixed crystal ratio, and AlN mixed crystal ratio, respectively. Among these Group 3-5 compound semiconductors, those containing InN in a mixed crystal ratio of 10% or more are particularly important for display applications because the emission wavelength in the visible region can be adjusted according to the InN mixed crystal ratio.
[0003]
Examples of the method for producing the Group 3-5 compound semiconductor include molecular beam epitaxy (hereinafter sometimes referred to as MBE) method, metal organic vapor phase epitaxy (hereinafter also referred to as MOVPE) method, and hydride vapor phase. Examples include a growth (hereinafter sometimes referred to as HVPE) method. Among these methods, the MOVPE method is important because it enables uniform crystal growth over a large area.
[0004]
By the way, the compound semiconductor needs to be grown at a higher temperature than other compound semiconductors such as GaAs, and the supply amount of the Group 5 material needs to be greatly increased compared to the Group 3 material. Moreover, it is difficult to obtain a high-quality crystal because there is no appropriate lattice-matching substrate for further epitaxial growth.
[0005]
As a result of intensive studies on a method for producing a Group 3-5 compound semiconductor, the present inventors have conducted a process of stopping the supply of the Group 3 raw material until the next layer is grown after the compound semiconductor layer is grown. By adding a carrier gas or a carrier gas and a Group 5 source material without supplying a Group 3 source material between the first layer growth step and the second layer growth step It has been found that a high-quality group 3-5 compound semiconductor can be produced with good reproducibility, and this method has already been proposed (Japanese Patent Laid-Open No. 9-36429).
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for growing a higher-quality Group 3-5 compound semiconductor with good reproducibility.
[0007]
[Means for Solving the Problems]
After that, as a result of further studies, the present inventors have supplied a specific Group 3 material called an In material before and / or after growing the Group 3-5 compound semiconductor layer, The present inventors have found that a higher quality Group 3-5 compound semiconductor can be obtained with good reproducibility.
[0008]
That is, the present invention provides [1] group 3-5 by a metal organic chemical vapor deposition method represented by the general formula In _x Ga _y N (x + y = 1, 0 < x < 1, 0 < y <1). In the compound semiconductor manufacturing method, the In source material, the Group 5 source material, and the carrier gas N ₂ are supplied without growing the substrate temperature from the InGaN layer growth temperature after growing the InGaN layer. A method for producing a Group-5 compound semiconductor is provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail.
The group 3-5 compound semiconductor in the present invention is represented by the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1). It is a group 3-5 compound semiconductor.
[0011]
The present invention produces a laminated structure of layers made of a group 3-5 compound semiconductor represented by the general formula InxGayAlzN (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1). In this case, the In raw material is supplied before and / or after the growth of the layer made of the Group 3-5 compound semiconductor.
Here, before growing the Group 3-5 compound semiconductor, after growing the Group 3-5 compound semiconductor, for example, before the production of the laminated structure, the growth interruption process during the growth of each layer during the production of the laminated structure The process after manufacture of a laminated structure is mentioned. Among these steps, the method of supplying the In raw material particularly in the growth interruption step shows a remarkable effect.
In the growth interruption step, the In raw material may be supplied at any time during this step. For example, immediately after the growth is completed, immediately before the growth is started, or at an arbitrary point in the growth interruption process. Of course, the In raw material may be supplied throughout the entire growth interruption step, or may be supplied intermittently.
[0012]
In these steps, if the growth condition of the layer made of a Group 3-5 compound semiconductor is not appropriate, In metal or InN may be deposited on the crystal surface. In general, the higher the substrate temperature, the lower the amount of In raw material supplied, the lower the pressure in the reactor, and the higher the hydrogen partial pressure or ammonia partial pressure in the reactor, the more likely they are to precipitate. is there. On the other hand, when the supply of the In raw material is too small, the effects of the present invention may not be sufficiently exerted. Therefore, the supply of the In raw material is preferably adjusted so that the partial pressure in the supplied raw material gas including the carrier gas is 1 × 10 ⁻⁶ atm or more and 0.01 atm or less. The time for supplying the In raw material is not particularly limited. However, if the supply time is too short, the effect of the present invention may not be sufficiently exhibited.
[0013]
The present invention is particularly preferably applied to the case of producing a layer containing In as a constituent element. In this case, the crystallinity of the layer is greatly improved, and a particularly preferable result is obtained. Among them, particularly preferable results are obtained when the layer thickness is a very thin layer of about several atomic layers, for example, 5 to 90 mm.
[0014]
In the MOVPE method of the present invention, the following raw materials can be used.
As a Group 3 raw material, for example, trimethylgallium [(CH ₃ ) ₃ Ga, hereinafter may be referred to as TMG. ], Triethylgallium [(C ₂ H ₅ ) ₃ Ga, hereinafter sometimes referred to as TEG. ] Trialkylgallium represented by the general formula R ₁ R ₂ R ₃ Ga (where R ₁ , R ₂ , R ₃ represent lower alkyl groups); trimethylaluminum [(CH ₃ ) ₃ Al ], Triethylaluminum [(C ₂ H ₅ ) ₃ Al, hereinafter TEA. ], General formula R ₁ R ₂ R ₃ Al such as triisobutylaluminum [(i-C ₄ H ₉ ) ₃ Al] (wherein R ₁ , R ₂ and R ₃ represent a lower alkyl group). Trialkylaluminum represented; trimethylamine allane [(CH ₃ ) ₃ N: AlH ₃ ]; trimethylindium [(CH ₃ ) ₃ In, hereinafter referred to as “TMI”. ], General formula R ₁ R ₂ R ₃ In such as triethylindium [(C ₂ H ₅ ) ₃ In] (wherein R ₁ , R ₂ and R ₃ represent lower alkyl groups). Trialkylindium such as trialkylindium and diethylindium chloride [(C ₂ H ₅ ) ₂ InCl] in which 1 to 3 alkyl groups are exchanged with a halogen atom, general formula InX such as indium chloride [InCl] (where X is a halogen atom) Trihalogenation represented by the general formula InX ₁ X ₂ X ₃ (wherein X ₁ , X ₂ , and X ₃ represent halogen atoms) such as indium halide and indium trichloride [InCl ₃ ] represented by Examples include indium. Examples of a method for supplying InX include a method of reacting a mixed gas of trialkylindium and hydrogen chloride gas at a high temperature, a method of reacting indium metal with hydrogen chloride at a high temperature, and the like. These may be used alone or in combination.
[0015]
Examples of Group 5 materials include ammonia, hydrazine, methyl hydrazine, 1,1-dimethylhydrazine, 1,2-dimethylhydrazine, t-butylamine, and ethylenediamine. These may be used alone or in combination. Among these raw materials, ammonia and hydrazine are preferable because they do not contain carbon atoms in their molecules and thus cause less carbon contamination in the semiconductor.
[0016]
As a crystal growth apparatus for a Group 3-5 compound semiconductor by the MOVPE method of the present invention, one having a known structure can be used. Specifically, a material gas sprayed from the upper part of the substrate and a material gas sprayed from the side of the substrate can be used. In these, the substrate is disposed approximately upward, but conversely, a substrate disposed downward can also be used. In this case, a material supplied from the lower part of the substrate or a material sprayed from the side of the substrate can be mentioned. In these reactors, the angle of the substrate does not need to be precisely horizontal, and includes cases where it is almost vertical or completely vertical. A typical example is shown in FIGS. The same applies to a growth apparatus that can process a plurality of substrates simultaneously by applying the arrangement of these substrates and gas supply.
[0017]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited to these Examples.
[0018]
Example 1 and Comparative Example 1
On the sapphire 3 (0001) surface, hydrogen is used as a carrier gas, ammonia, TMG, and silane are used as raw materials, and GaN is grown as a low temperature buffer layer 4 at 550 ° C. by about 50 nm, and then doped with Si at 1040 ° C. A type GaN layer 5 was grown to about 3 μm, and a non-doped GaN layer 6 was grown to 0.25 μm.
Next, the temperature was lowered to 775 ° C., and a 25 nm GaN layer 7 doped with Si using TEG, TMI, silane, and ammonia and a 3 nm InGaN layer 8 were grown five times by using nitrogen as a carrier gas. The detailed growth procedure is as follows. After growing GaN doped with Si for 5 minutes using ammonia, TEG and silane, the supply of TEG and silane is stopped and the Group 3 raw material is not supplied. Growth of InGaN layer using TEG, TMI, and ammonia for 30 seconds, supply of TEG is stopped, growth middle stage process for supplying only TMI as a Group 3 material for 5 seconds, and growth middle stage process for which supply of TMI is also stopped for 5 minutes It was.
[0019]
After repeating this procedure five times, an Al _0.2 Ga _0.8 N layer 9 was grown by 250 mm. Further, the carrier gas is again hydrogen, the temperature is raised to 1040 ° C., TMG, ammonia, bisethylcyclopentadienylmagnesium [(C ₂ H ₅ C ₅ H ₄ ) ₂ Mg, hereinafter referred to as ECp ₂ , as a p-type dopant material. Sometimes referred to as Mg. ] Was used to grow the p-type GaN layer 10 by 200 nm. After the growth was completed, the substrate was taken out and heat-treated at 800 ° C. in nitrogen to make the p-type GaN layer 12 a low-resistance p-type layer.
Further, as a comparative example, an LED epitaxial wafer was produced in the same manner as in Example 1 except that only the TMI material was supplied as the Group 3 material, instead of supplying the Group 3 material.
[0020]
A NiAu p electrode and an Al n electrode were formed on the sample obtained above. When a forward current of 20 mA was passed through the LED samples thus obtained, all the samples showed clear blue light emission. When the luminances of the samples of Example 1 and Comparative Example 1 were compared, the luminance of Example 1 was 30% higher than that of Comparative Example 1 at the maximum value.
When the satellite reflection of the multiple quantum well structure by X-ray diffraction was evaluated for both samples, no difference was found between the two samples, and it was found that there was no difference in the film thickness and In composition of the quantum well layer and the barrier layer.
[0021]
【The invention's effect】
According to the present invention, the crystal quality of the nitride-based compound semiconductor can be greatly improved. For this reason, since the characteristics of various devices using nitride compound semiconductors, in particular, light emitting elements can be dramatically improved, they are extremely useful and have great industrial value.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of the structure of a reaction furnace that can be used in the present invention.
FIG. 2 is a cross-sectional view showing an example of the structure of a reaction furnace that can be used in the present invention.
3 shows a structure of a light-emitting element manufactured in Example 1. FIG.
[Explanation of symbols]
1. . . 1. Susceptor . . Substrate 3. . . 3. Sapphire substrate . . 4. Buffer layer . . n-type GaN layer 6. . . 6. Non-doped GaN layer . . Si-doped GaN layer8. . . InGaN layer 9. . . AlGaN layer 10. . . p-type GaN layer

Claims (2)

In the method for producing a group 3-5 compound semiconductor represented by the general formula In _x Ga _y N (x + y = 1, 0 < x < 1, 0 < y <1) by metal organic vapor phase epitaxy, A method for producing a Group 3-5 compound semiconductor, comprising: supplying a Group 5 source material and carrier gas N ₂ without growing the substrate temperature from the InGaN layer growth temperature after growing the InGaN layer.   The manufacturing method according to claim 1, wherein the In raw material is trimethylindium.

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