JPH06216409A - Growth method of single-crystal semiconductor nitride - Google Patents

Abstract

PURPOSE:To provide a method, in which a single-crystal InAlGaN layer having excellent crystallizability is grown on a substrate first in order to form a light- emitting device utilizing a semiconductor nitride in double-hetero structure. CONSTITUTION:A single-crystal semiconductor nitride layer shown in general formula InXAlYGa1-X-YN (where X<0<1 an Y<0<1 hold) is grown on a substrate through a vapor growth method in the title method, a substrate, a substrate, in which a buffer layer consisting of GaZAl1-ZN (0<=Z<=1) is formed onto sapphire and a single-crystal layer composed of GaN onto the buffer layer, is employed as the substrate, and the semiconductor nitride single-crystal layer is grown on the single-crystal GaN layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a nitride semiconductor single crystal layer used in a light emitting device such as an ultraviolet light emitting diode, a blue light emitting diode and a laser diode, and more particularly to a quaternary mixed crystal indium aluminum gallium nitride Below InA
lGaN) and a method for growing a single crystal layer.

[0002]

2. Description of the Related Art Nitride semiconductors, especially quaternary mixed crystal In _X A
l _Y Ga _1-XY N has a band gap energy of about 2 eV to 6 eV, a-axis lattice constant of about 3.1 angstroms to 3.5 angstroms, and a direct transition, depending on the composition ratio of X and Y. In addition, it is attracting attention as a material for light emitting devices such as ultraviolet, blue and laser diodes. However, at the moment, I
Since a high-quality single crystal layer of nAlGaN has not been grown, a light emitting device using this material has not been put to practical use.

InAlGaN can be grown by a vapor phase growth method such as a metal organic compound vapor phase growth method and a molecular beam epitaxy method. According to these methods, conventionally, InAlGaN grown on a substrate is not in a single crystal but in a polycrystalline state. Therefore, this InAlGa
Other types of nitride semiconductors on N polycrystal, for example, binary GaN, AlN, ternary InGaN, AlGa
When N and quaternary mixed crystal InAlGaN are laminated to form a heterostructure, the crystallinity of InAlGaN formed on the substrate is poor, and therefore binary crystal and ternary mixed crystal having excellent crystallinity It was not possible to form a crystal semiconductor or a quaternary mixed crystal nitride semiconductor layer. Because conventionally, sapphire is usually used for the substrate, and this sapphire substrate and InAlGa
Since the lattice constant mismatch with N was 11% or more, an InAlGaN layer having excellent crystallinity could not be obtained.

In order to improve the crystallinity of the nitride semiconductor grown on the substrate, various methods have been conventionally proposed.
For example, Japanese Patent Publication No. 59-48794 discloses a method of providing a buffer layer made of AlN on a sapphire substrate. Further, JP-A-2-21620 discloses a method of growing on the M-plane of a sapphire substrate.
No. 3233 discloses a method of growing on the R surface of a sapphire substrate. In addition, JP-A-4-209577
The publication discloses a method of using ZnO for a substrate. All of these methods have been proposed to alleviate the lattice constant mismatch between the substrate and the nitride semiconductor,
In all of these methods, a nitride semiconductor having excellent crystallinity can only be obtained up to a binary mixed crystal of GaN, AlN, etc. Therefore, in a light emitting device using a nitride semiconductor,
The only one that has been put to practical use is a so-called homojunction MIS structure GaN light emitting diode in which an n-type GaN layer and a high-resistance i-type GaN layer doped with a p-type dopant are stacked on the substrate. unknown.

[0005]

If a quaternary mixed crystal InAlGaN having excellent crystallinity can be grown on a substrate, a binary mixed crystal, a ternary mixed crystal, or a quaternary mixed crystal can be grown on it. Growing a nitride semiconductor becomes easy because the lattice constant irregularity of the nitride semiconductor becomes extremely small, and a light emitting device having a double hetero structure, which has been extremely difficult in the past, can be realized. Therefore, the present invention has been made in view of such circumstances, and since the light emitting element using the nitride semiconductor has the double hetero structure, the quaternary mixed crystal InAlGaN having excellent crystallinity is first formed on the substrate. It is an object to provide a method for growing a single crystal layer.

[0006]

Means for Solving the Problems Quaternary mixed crystal InAlGaN
In growing the single crystal layer of, the present inventor has found that the above problem can be solved by growing the single crystal layer on a substrate having GaN having excellent crystallinity. That is, the growth method of the present invention uses the general formula In _X Al _Y Ga _1-XY N (where X <0 <1 and Y <0 <by a vapor phase growth method.
1) A method for growing a nitride semiconductor single crystal layer represented by 1), wherein the substrate is Ga _Z Al ₁ -Z on sapphire.
A substrate in which a buffer layer made of N (0 ≦ Z ≦ 1) and a single crystal layer made of GaN is formed on the buffer layer is used, and the nitride semiconductor single crystal layer is formed on the GaN single crystal layer. It is characterized by growing.

In the growth method of the present invention, the vapor phase epitaxy method includes the organometallic compound vapor phase epitaxy method (hereinafter,
This is called the MOCVD method. ), A molecular beam epitaxy method can be preferably used. For example, in the method using MOCVD, an organometallic compound gas such as trimethylgallium, trimethylindium, and trimethylaluminum is used as a metal element source, and a gas such as ammonia and hydrazine is used as a nitrogen source. Can be grown on a heated substrate in a reaction vessel to grow InAlGaN. The growth temperature is preferably in the range of 700 ° C to 1100 ° C,
If the temperature is 0 ° C. or lower, InAlGaN is likely to become polycrystalline, and if the temperature is 1100 ° C. or higher, InN similarly decomposes, so that InAlGaN of a quaternary mixed crystal tends to be difficult to be formed.

Buffer layer Ga _Z Al _1-Z N (0 ≦ Z ≦ 1)
Are necessary for improving the crystallinity of the GaN single crystal grown on the buffer layer. This buffer layer is disclosed in JP-B-59-48794 and JP-A-4-29.
Although not particularly different from the buffer layer disclosed in Japanese Patent No. 7023, a GaN single crystal layer having a crystallinity superior to that of a GaN buffer layer of Z = 1 is preferred to an AlN buffer layer of Z = 0. Can be obtained.

The single crystal layer formed on the buffer layer is Ga
Must be N. In particular, the crystallinity of the GaN must be excellent, and as a means for evaluating the crystallinity, in the X-ray diffraction measurement by the X-ray double crystal method (hereinafter referred to as X-ray rocking curve measurement), (0002). It is preferable that the half width of the diffraction peak of the (1) plane is 15 minutes or less, more preferably 10 minutes or less. An InAlGaN single crystal layer can be grown on a GaN single crystal even if its half-value width is larger than 15 minutes.
More excellent InAl by selecting N single crystal layer
A GaN single crystal layer can be grown. However, as in the prior art, a part of Ga of this GaN single crystal layer is Al,
Substitution with In or the like is not preferable because the crystallinity of the GaN single crystal layer deteriorates.

[0010]

According to the conventional method, an AlN buffer layer is formed on the sapphire substrate to reduce the lattice constant mismatch between sapphire and the nitride semiconductor, and quaternary mixed crystal InAlGaN is directly formed on the AlN buffer layer. Alternatively, the substrate was changed to a substrate having a lattice constant close to that of the nitride semiconductor, and the same InAlGaN was directly grown on the substrate, so that only polycrystalline InAlGaN was obtained.

On the other hand, the present invention is different from the prior art in that a buffer layer is formed on sapphire, and a GaN single crystal layer having excellent crystallinity is first formed on the buffer layer. is there. Next, the sapphire, the buffer layer, and the GaN single crystal layer are considered as one substrate, and the GaN single crystal plane having the highest crystallinity on this substrate has the smallest lattice constant irregularity and is made of the same nitride semiconductor as GaN. Quaternary mixed crystal I
The growth was successful for the first time by growing nAlGaN. It is speculated that this is possible because the same nitride semiconductor is stacked on the nitride semiconductor having excellent crystallinity.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The growth method of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows the MOC used in the growth method of the present invention.
FIG. 3 is a schematic cross-sectional view showing the configuration of the main part of the VD device, showing the structure of a reaction part and a gas system diagram communicating with the reaction part. Reference numeral 1 is a reaction vessel connected to a vacuum pump and an exhaust device, 2 is a susceptor for mounting a substrate, 3 is a heater for heating the susceptor, 4 is a control shaft for rotating and vertically moving the susceptor, and 5 is a diagonal to the substrate. , Or a quartz nozzle that supplies the raw material gas horizontally, and 6 is a conical device that presses the raw material gas against the substrate surface by supplying the inert gas vertically toward the substrate to bring the raw material gas into contact with the substrate. A quartz tube, 7 is a substrate. Organometallic compound sources such as TMG (trimethylgallium), TMI (trimethylindium), and TMA (trimethylaluminum) are vaporized by a small amount of bubbling gas and supplied into the reaction vessel by a carrier gas that is a main gas. Although not shown in particular, the flow rates of the source gases and the carrier gas are controlled by a mass flow controller (MFC) installed in each gas line.

Example 1 First, a well-cleaned sapphire plate 7 was set on the susceptor 2, the inside of the reaction vessel was evacuated, and then hydrogen was supplied to sufficiently replace the inside of the reaction vessel with hydrogen. Next, while flowing hydrogen from the quartz nozzle 5, the temperature is raised to 1050 ° C. by the heater 3 and kept for 20 minutes to clean the sapphire plate 7.

Subsequently, the temperature is lowered to 510 ° C., and the quartz nozzle 5 is used to feed ammonia (NH ₃ ) 4 liters / minute and T
Hold MG for 1 minute while flowing MG at 27 × 10 ⁻⁶ mol / min and hydrogen as carrier gas at 2 liter / min.
The aN buffer layer is grown to about 200 Å. During this time, hydrogen is supplied from the conical quartz tube 7 to 10
Continue to flow liters / minute and nitrogen at 10 liters / minute and slowly rotate susceptor 2.

After growth of the GaN buffer layer, only TMG is stopped and the temperature is raised to 1020.degree. Temperature is 1020
When the temperature reaches ℃, hydrogen is also used as a carrier gas for TMG.
At 60 × 10 ⁻⁶ mol / min for 30 minutes to grow,
The aN single crystal layer is grown to about 2 μm. After growing the GaN single crystal layer, the apparatus is cooled, the substrate is taken out of the reaction container, and Ga is removed.
When the X-ray rocking curve of the N single crystal layer was measured, the full width at half maximum was 5 minutes, and it was confirmed that the crystallinity was excellent.

After measuring the X-ray rocking curve, the substrate was set again on the susceptor in the reaction vessel, the inside of the susceptor was evacuated and replaced with nitrogen, and then the temperature was raised to 800 ° C. while flowing ammonia gas. When the temperature reached 800 ° C, nitrogen was 2 liters / minute and TMG was 2 × 10 ^-6 mol / min.
Min, TMI 1 × 10 ^-5 mol / min, TMA 2 × 1
The InAlGaN layer is grown for 60 minutes while flowing 0 ^-7 mol / min and 4 liter / min of ammonia.

After the growth, the wafer was taken out from the reaction container, and the X-ray rocking curve of the obtained InAlGaN single crystal layer was measured. As a result, a peak was found at a composition of In0.2Al0.1Ga0.7N. The full width at half maximum of the peak was 6 minutes. From this, this In0.2Al0.1Ga
It shows that the crystallinity of 0.7N is very excellent.
Moreover, He-Cd is deposited on the In0.2Al0.1Ga0.7N layer at room temperature.
When laser was irradiated and the photoluminescence spectrum was measured, strong ultraviolet emission having a peak at around 360 nm was shown.

[Embodiment 2] In0.2Al was formed on the GaN single crystal layer in the same manner as in Embodiment 1 except that a substrate having a GaN single crystal layer with a half width of 10 minutes was used.
When a 0.1 Ga 0.7 N single crystal layer was grown, the obtained I
The half-width of the X-ray rocking curve of the n0.2Al0.1Ga0.7N single crystal layer was 8 minutes, indicating excellent crystallinity.

[Example 3] In0.2Al was formed on the GaN single crystal layer in the same manner as in Example 1 except that the substrate in which the GaN single crystal layer had a half value width of 15 minutes was used.
When a 0.1 Ga 0.7 N single crystal layer was grown, the obtained I
The full width at half maximum of the X-ray rocking curve of the n0.2Al0.1Ga0.7N single crystal layer was 10 minutes, which also showed excellent crystallinity.

Example 4 After the growth of the GaN single crystal layer in Example 1, the substrate is not taken out of the reaction vessel and the temperature is continuously lowered to 800 ° C. When it reaches 800 ℃, TM
An InAlGaN layer is grown for 60 minutes in the same manner as in Example 1 except that the flow rate of A is 4 × 10 ⁻⁷ mol / min.

After the growth, the wafer was taken out from the reaction container, and the X-ray rocking curve of the obtained InAlGaN single crystal layer was measured. As a result, a peak was found at a composition of In0.2Al0.2Ga0.6N. The half-width of the peak is 10 minutes, and In0.2Al, which also has excellent crystallinity
It was shown that 0.2 Ga0.6 N was obtained.

Comparative Example In Example 1, after growing the GaN buffer layer, the GaN buffer layer was grown on the GaN buffer layer.
InAlGaN is directly grown under the same conditions as in Example 1.

After the growth, when the X-ray rocking curve of the obtained InAlGaN layer was measured, only a broad peak was detected, and even if the photoluminescence measurement was carried out in the same manner as in Example 1, the InAlGaN layer showed no difference. Was not observed. InAlG obtained from this
It was found that aN was grown in an amorphous state.

[0024]

As described above, according to the growth method of the present invention, by growing on a substrate having a GaN single crystal layer having excellent crystallinity, it is possible to obtain excellent crystallinity which was conventionally difficult. An original mixed crystal InAlGaN single crystal layer can be obtained. Therefore, a binary mixed crystal, a ternary mixed crystal, or a quaternary mixed crystal nitride semiconductor can be easily stacked on this InAlGaN, and a nitride semiconductor light emitting device having a double hetero structure can be obtained. Its industrial utility value is great.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the configuration of the main part of a MOCVD apparatus used in an embodiment of the present invention.

[Explanation of symbols]

1 ... Reaction container 2 ... Susceptor 3 ... Heater 4 ... Control shaft 5 ...・ Quartz nozzle 6 ・ ・ ・ ・ ・ ・ ・ ・ Conical quartz tube 7 ・ ・ ・ ・ ・ ・ Sapphire plate

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[Procedure amendment]

[Submission date] March 5, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

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[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

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[0006]

Means for Solving the Problems Quaternary mixed crystal InAlGaN
In growing the single crystal layer of, the present inventor has found that the above problem can be solved by growing the single crystal layer on a substrate having GaN having excellent crystallinity. That is, the growth method of the present invention uses the general formula In _X Al _Y Ga _1-XY N (where 0 <X <1, 0 <Y <
1) A method for growing a nitride semiconductor single crystal layer represented by 1), wherein the substrate is Ga _Z Al ₁ -Z on sapphire.
A substrate in which a buffer layer made of N (0 ≦ Z ≦ 1) and a single crystal layer made of GaN is formed on the buffer layer is used, and the nitride semiconductor single crystal layer is formed on the GaN single crystal layer. It is characterized by growing.

Claims (2)

[Claims] 1. A general formula In is formed on a substrate by a vapor deposition method.
A method of growing a nitride semiconductor single crystal layer represented by _X Al _Y Ga _1-XY N (where X <0 <1 and Y <0 <1), wherein Ga is formed on sapphire on the substrate. _Z Al _1-Z N (0
Using a substrate having a buffer layer of ≦ Z ≦ 1) and a single crystal layer of GaN formed on the buffer layer, the nitride semiconductor single crystal layer is grown on the GaN single crystal layer. A method for growing a nitride semiconductor single crystal layer, comprising: 2. The GaN single crystal layer has a half width of a diffraction peak of a (0002) plane of 15 minutes or less in an X-ray diffraction measurement by an X-ray double crystal method. Method for growing nitride semiconductor single crystal layer.