JP2000203995A - Growing method of compound semiconductor crystal, compound semiconductor crystal grown by the method and compound semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a growing method of a GaN compd. semiconductor crystal in which the crystal can be grown along the 11-24} planer direction as the growing direction where the inner electric field is zero, and to provide a GaN compd. semiconductor crystal obtd. by this growing method, and a semiconductor device using the GaN compd. semiconductor crystal substrate. SOLUTION: In the growing method of a GaN compd. semiconductor crystal on a rare earth 13 (3B) perovskite crystal substrate containing one or more kinds of rare earth elements, the substrate is subjected to first cleaning with an org. solvent and to second cleaning with an inorg. acid as pretreatment so that the substrate surface has a surface state to grow the 11-24} plane of a GaN compd. semiconductor crystal. Concretely, the first cleaning process using an org. solvent is carried out (1) by boiling the substrate in trichloroethylene and then degreasing under untrasonics in acetone and methanol. Or, the process is carried out by (2) ultrasonic cleaning using acetone and methanol. In the second cleaning using an inorg. acid, the substrate is subjected to etching in a mixture soln. having the volume ratio of phosphoric acid to sulfuric acid of 1:3. The process (1) is preferably carried out in an environment over 80 deg.C.

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 GaN-based compound semiconductor crystal used for a semiconductor device such as an optical device and an electronic device, and to a method for growing the same.
The present invention relates to a GaN-based compound semiconductor crystal and a GaN-based compound semiconductor device, and more particularly to a method of growing a GaN-based compound semiconductor crystal on a rare earth 13 (3B) group perovskite crystal substrate and a GaN-based compound semiconductor grown by the growth method. The present invention relates to a crystal and a GaN-based compound semiconductor device.

[0002]

BACKGROUND OF THE INVENTION GaN-based compound semiconductor _{(In x Ga y Al 1-} xy N, 0
≦ x, y: x + y ≦ 1) is expected as a light-emitting and light-receiving element having a wide bandgap, a short wavelength, and an environment-resistant element, and has been widely studied. However, since there is no large bulk crystal in the GaN system, a thin film crystal by heteroepitaxy on a heterogeneous crystal substrate represented by sapphire has been used. However, in many cases, there is a problem that the lattice mismatch between the heterogeneous crystal plate used for the substrate and the GaN-based compound semiconductor thin film grown thereon is large.

[0003] As one of the excellent hetero-crystal substrates for heteroepitaxy of GaN-based compound semiconductors, rare-earth
A rare earth 13 (3B) group perovskite represented by Ga perovskite has been proposed (Japanese Patent Application No. 7-526233). When this type of crystal is used for the substrate, for example, NdGaO ₃ and GaN have a lattice mismatch of about 1.2%, which is much smaller than sapphire, and compared to SiC used as a substitute for sapphire. However, it has a small lattice constant difference and is suitable for heteroepitaxy.

[0004] When a GaN-based compound semiconductor crystal is grown on a rare-earth 13 (3B) group perovskite crystal substrate, the grown crystal plane is usually (0001). Various devices using a compound semiconductor are manufactured. For example, a light emitting diode (LE
In D) and laser diodes (LD), InGaN / Ga
A quantum well structure using N or the like as a material system is employed.

[0005]

However, (0001)
When a strained quantum well is formed on a plane, a piezo electric field (internal electric field) is generated due to the presence of in-plane biaxial stress, and this piezo electric field affects characteristics such as luminous efficiency and luminous wavelength. is there. That is, since the nitride-based semiconductor has a large piezoelectric constant, it is easily affected by an internal electric field,
In a light-emitting element using a nitride-based semiconductor, there arises a problem that the light-emitting efficiency is reduced or the light-emitting wavelength is changed.

However, regarding the piezo electric field, according to Takeuchi et al., It has been reported that it is possible to control the generation of the piezo electric field by controlling the orientation of the growth plane (the 58th Annual Meeting of the Japan Society of Applied Physics). Proceedings No.1, Akita, 1997
Year p.255). According to it, {01-12}, {11-24}, {01-1
By setting each plane orientation such as {0} and {2-1-10} to the growth direction, the generation of the piezoelectric field can be reduced to zero,
If strained quantum wells are formed on these surfaces, it is possible to greatly improve the characteristics of the light emitting and light receiving elements. On the other hand, it is also clear that the (0001) plane obtained as a growth plane is the plane where the piezo electric field is the largest.

However, although verification has progressed theoretically, it is difficult to accurately control the growth plane orientation as a practical crystal growth technique. There have been no successful cases.

Therefore, according to the present invention, the internal electric field becomes zero {11-
A method for growing a GaN-based compound semiconductor crystal capable of growing a crystal with the {24} plane orientation as a growth direction, a GaN-based compound semiconductor crystal obtained by the growth method, and a substrate of the GaN-based compound semiconductor crystal It is an object to provide a semiconductor device.

[0009]

Means for Solving the Problems Conventionally, for example, the (011) plane N
When GaN is epitaxially grown by using dGaO ₃ as a substrate, boiling cleaning with trichloroethylene and ultrasonic cleaning with acetone and methanol are performed as pretreatment steps, followed by etching with an acid, and then set in an epitaxial growth apparatus. Was doing the growth process,
In that case, the growth direction of GaN was (0001), and the generation of the piezoelectric field was largest.

Therefore, the present inventor focused on pretreatment (cleaning and etching treatment) when growing using an NdGaO ₃ crystal as a substrate, and by changing the conditions of the pretreatment, the growth direction was changed and the piezo electric field was reduced. The intense experiment was conducted based on the inference that the generation could be smaller than that of the (0001) plane.

As a result, the inventors have concluded that it is possible to obtain a crystal plane of a GaN-based compound semiconductor capable of suppressing generation of a piezoelectric field by the following growth method, and have completed the present invention.

That is, Ga is deposited on a rare earth 13 (3B) group perovskite crystal substrate containing one or more kinds of rare earth elements.
In the method of growing an N-based compound semiconductor crystal, the substrate is subjected to a first cleaning with an organic solvent and a second cleaning with an inorganic acid as pretreatment, and the substrate surface has a {11- 24} plane was grown. This makes it possible to incorporate the element on the {11-24} plane, and in the GaN-based compound semiconductor device, it is possible to reduce the generation of a piezoelectric field that adversely affects the device characteristics to zero.

[0013] The first washing with the organic solvent is as follows.
Degreasing cleaning in which ultrasonic cleaning with acetone and methanol or the like is performed after boiling cleaning with trichloroethylene or the like, or ultrasonic cleaning with acetone and methanol or the like can be used. The second washing with the inorganic acid is etching with a mixed solution in which the volume ratio of phosphoric acid: sulfuric acid is 1: 3.
It is good to be carried out under a temperature environment exceeding. This allows
A good {11-24} plane can be obtained as a growth plane.

Further, the crystal plane of the perovskite crystal is
Any one of {011}, {100}, and {101} planes, and the perovskite crystal is composed of the rare earth 13 (3
B) At least one of Al, Ga, and In is included as a group element.

Further, in the method of growing a GaN-based compound semiconductor crystal, it is preferable to grow a thick film by a hydride vapor phase epitaxial growth method. As a result, it grew
The GaN-based compound semiconductor crystal thick film can be separated from the perovskite crystal substrate, and the freestanding {11-
A 24} -plane GaN-based compound semiconductor crystal wafer can be obtained.

Furthermore, it is possible to obtain a GaN-based compound semiconductor crystal having a {11-24} plane grown by applying the above-mentioned method for growing a GaN-based compound semiconductor crystal, and to configure a semiconductor device using this as a substrate. be able to. This allows
A semiconductor device having good characteristics can be manufactured.

Here, the {11-24} plane represents a plane equivalent to the (11-24) plane. Further, trichlorethylene and the like means trichlorethylene or a substance having the same effect, and acetone and methanol are also referred to.
It means the same thing.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below based on experiments.

A (011) plane NdGaO ₃ crystal substrate having a thickness of 350 μm was used as a substrate, and GaN was grown on this substrate. As shown in FIG. 1, the conventional pretreatment is boiling washing S1 with trichloroethylene for 5 minutes, organic washing S2 with acetone for 5 minutes,
Organic washing with methanol S3 for 5 minutes, washing with running water
After performing S4 for 5 minutes and etching S5 with a mixed solution of phosphoric acid and sulfuric acid (volume ratio 1: 3) for 1 minute, washing with water S6 and drying.

In this experiment, the pretreatment was performed under the conditions shown in Table 1 with the presence / absence of boiling washing S1 using trichloroethylene and the processing temperature of etching S5 using a mixed solution of phosphoric acid and sulfuric acid (volume ratio 1: 3). Then, a GaN crystal was grown.

[0021]

[Table 1] All GaN crystal growth was performed as follows.

First, the preprocessed substrate is set on a quartz wafer holder in a hydride VPE (Vapor Phase Epitaxy, vapor phase epitaxial growth) apparatus, and the temperature of the substrate is raised to 600 ° C. while flowing nitrogen gas. The temperature of the Ga raw material was raised to and maintained at 85 ° C. Then, HCl gas diluted with nitrogen gas is flowed from the upstream side of the Ga raw material,
An NH ₃ gas was flowed immediately above and near the substrate, bypassing the raw material, and a first GaN layer was grown on the substrate for 10 minutes. continue,
The temperature of the substrate is raised to 1000 ° C. and maintained, and the second layer of GaN is
After growing for 0 minutes and cooling, the wafer was taken out.

The first layer is a protective film for the substrate for growing the second layer, and has a very small thickness of the order of nm. The thickness of the second layer was 100 μm, and as a whole, it was a flat mirror-surface epitaxial film with no abnormal growth on the surface.

Table 2 shows the results of X-ray diffraction observation of this epitaxial film. By performing the pretreatment under the conditions 3, 4, 5, and 6, a (11-24) plane having good film quality could be obtained.

That is, in the pretreatment step, when washing by boiling with trichloroethylene is performed, phosphoric acid +
By performing etching S5 with a mixed solution of sulfuric acid in a temperature environment higher than 80 ° C., or by omitting boiling washing with trichloroethylene, (11-24)
It turned out to grow the surface.

The conventional pretreatment was performed under the condition 2, and the obtained growth plane was a (0001) crystal.

[0027]

[Table 2] Although the invention made by the inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments. For example, the organic solvent used for boiling washing can be replaced with ethyl lactate, limonene or the like without being limited to trichlorethylene, and washing can be performed if the boiling time is 1 minute or more. Acetone or methanol used for organic cleaning can be replaced by a water-soluble organic solvent such as ethanol or isopropyl alcohol. Further, the etching time with the mixed solution of phosphoric acid and sulfuric acid is not limited to 5 minutes, and the same result can be obtained if it is 1 minute or more.

[0028]

The effects obtained by the invention disclosed in the present application will be briefly described as follows.

That is, it is possible to grow a {11-24} plane GaN-based compound semiconductor crystal, and use the {11-24} plane GaN-based compound semiconductor crystal as a substrate to form an element on the {11-24} plane. To form a strained quantum well structure, the generation of a piezoelectric field can be suppressed, and a light-emitting and light-receiving element having excellent characteristics can be manufactured.

[Brief description of the drawings]

FIG. 1 is a flowchart of a pretreatment step.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G077 AA03 AB02 BE11 BE15 DB04 DB05 EC03 ED05 ED06 EE04 HA02 HA06 TB02 TB03 TK01 TK06 TK10 5F043 AA40 BB21 BB27 DD02 DD07 GG06 5F045 AB14 AC12 AC13 AC15 AD10 AD14 CA13 CB13 DQ08 EB13 GH08 HA01 HA04

Claims (10)

[Claims] 1. A method according to claim 1, wherein the substrate is made of a rare earth 13 (3B) group perovskite crystal containing one or more rare earth elements.
In the method for growing an N-based compound semiconductor crystal, a first cleaning with an organic solvent and a second cleaning with an inorganic acid are performed so that the surface state of the substrate can grow the {11-24} plane of the GaN-based compound semiconductor crystal. A method for growing a GaN-based compound semiconductor crystal, wherein washing is performed as a pretreatment. 2. The GaN-based compound according to claim 1, wherein the first cleaning with an organic solvent is a degreasing cleaning in which boiling cleaning with trichloroethylene or the like is performed and then ultrasonic cleaning with acetone, methanol, or the like. A method for growing a semiconductor crystal. 3. The second washing with the inorganic acid is performed at 80 ° C. with a mixed solution having a phosphoric acid: sulfuric acid volume ratio of 1: 3.
The method of growing a GaN-based compound semiconductor crystal according to claim 2, wherein the etching is performed in a temperature environment exceeding 300 ° C. 4. The method for growing a GaN-based compound semiconductor crystal according to claim 1, wherein the first cleaning with the organic solvent is ultrasonic cleaning with acetone, methanol, or the like. 5. The GaN-based compound semiconductor crystal according to claim 4, wherein the second cleaning with the inorganic acid is etching with a mixed solution having a phosphoric acid: sulfuric acid volume ratio of 1: 3. Growth method. 6. The growth crystal plane of the perovskite crystal is
The GaN according to any one of claims 1 to 5, wherein the GaN is any one of a {011} plane, a {100} plane, and a {101} plane.
Method for growing compound semiconductor crystal. 7. The rare earth 13
The method for growing a GaN-based compound semiconductor crystal according to any one of claims 1 to 6, wherein at least one of Al, Ga, and In is included as the (3B) group element. 8. The method of growing a GaN-based compound semiconductor crystal according to claim 1, wherein the thick film is grown by a hydride vapor phase epitaxial growth method. Growth method. 9. A GaN-based compound semiconductor having a {11-24} plane grown by applying the method of growing a GaN-based compound semiconductor crystal according to claim 1. Description: crystal. 10. A GaN-based compound semiconductor device comprising the GaN-based compound semiconductor crystal according to claim 9 as a substrate, and an element formed on the substrate.