JP2002293697A - METHOD OF GROWING GaN EPITAXIAL LAYER - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide epitaxial growth of GaN which is capable of growing a good-quality GaN crystal on a GaAs substrate. SOLUTION: This method of growing the GaN epitaxial layer includes a step of growing a GaN buffer layer 20 on the GaAs substrate 10, a step of heating up the GaAs substrate 10 from the temperature (for example, 550 deg.C) at which the GaN buffer layer 20 is formed up to the temperature (for example, 1,000 deg.C) at which the GaN is ought to be epitaxially grown within 35 minutes and a step of growing the GaN epitaxial layer 30 on the GaN buffer layer 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a blue-violet laser,
ED and G used for high frequency and high power electronic devices
The present invention relates to a method for epitaxially growing aN.

[0002]

2. Description of the Related Art It is difficult to grow a single crystal of GaN (gallium nitride), and a large bulk crystal has not been obtained so far. Recently, bulk crystals of several mm square have been obtained by melt growth under high temperature and high pressure, but are not at a stage where they can be put to practical use as substrates for electronic devices. Also, sublimation method or N
(a) Attempts have been made to grow in a melt, but even with these, large crystals cannot be obtained.

At present, the most technologically advanced method of manufacturing a GaN single crystal substrate is HVPE (Hydride Vapo).
r Phase Epitaxy) method on a sapphire substrate
This is a method of heteroepitaxially growing N. Since sapphire is chemically stable, it does not change even in a highly reactive environment of a GaN epitaxial growth atmosphere and is very easy to handle as a substrate.

However, this method using a sapphire substrate has a disadvantage that it is difficult to separate the grown GaN epitaxial layer from the sapphire substrate.

On the other hand, GaAs is a substrate that can be easily separated from a grown GaN epitaxial layer.
s substrate. GaAs is softer than sapphire and can be easily dissolved and removed with aqua regia or the like, so that GaAs can be easily removed from the epitaxial layer.

[0006]

SUMMARY OF THE INVENTION However, GaAs
When GaN is epitaxially grown on an s substrate, the following problems occur. That is, since GaAs is chemically unstable, it is used at a high temperature of 1000 ° C. or more and hydrogen,
Under a severe condition of normal epitaxial growth, which is usually performed in a reducing atmosphere using a mixed gas of ammonia and hydrogen chloride, the reaction and decomposition of the GaAs substrate itself proceed, and it is difficult to epitaxially grow GaN thereon.

In order to solve this problem, for example, Hasegawa et al. Of the University of Tsukuba proposed that 5 (5)
After forming a GaN buffer layer at 50 ° C.,
To grow a GaN intermediate layer of about 3 μm.
The temperature was raised to 000 ° C. to obtain a thick GaN film (199).
February 9). However, in this method, since the crystal quality of the obtained GaN thick film depends on the crystallinity of the intermediate layer, it is difficult to obtain a high-quality crystal, and it is time-consuming.

The present invention has been made to solve the above problems, and has as its object to provide an epitaxial growth of GaN that can grow a good-quality GaN crystal on a GaAs substrate.

[0009]

In order to achieve the above object, the present invention provides a method for growing a GaN buffer layer on a GaAs substrate, comprising: Heating the GaAs substrate within 35 minutes; and growing a GaN epitaxial layer on the GaN buffer layer.

According to the present invention, G is determined from the growth temperature of the buffer layer.
The temperature is raised to a temperature for growing the aN epitaxial layer in a short time of 35 minutes or less. Then, it is possible to prevent a reaction between GaAs and a gas such as NH ₃ used for growing GaN, and to prevent decomposition of GaAs due to heating, and the crystal quality of the GaAs substrate is not deteriorated even in the growth stage of the GaN epitaxial layer. . Therefore, the GaN epitaxial layer grown on such a GaAs substrate has good crystal quality.

In the method of growing a GaN epitaxial layer according to the present invention, the GaN buffer layer preferably has a thickness in a range of 200 Å to 2000 Å. When the buffer layer has such a thickness, lattice mismatch between the GaAs substrate and the GaN epitaxial layer can be reduced, and a favorable epitaxial layer can be obtained.

In the method of growing a GaN epitaxial layer according to the present invention, the growth temperature of the GaN buffer layer may be 4 or less.
The temperature is preferably in the range of 50 ° C to 600 ° C. With such a growth temperature, it is possible to provide a buffer layer that can reduce lattice mismatch between the GaAs substrate and the GaN epitaxial layer. Note that GaN is grown on the buffer layer. In the present invention, this growth is also called epitaxial growth.

In the method of growing a GaN epitaxial layer according to the present invention, the GaN epitaxial layer may have a thickness of 950.
It is preferable to carry out at a temperature of not less than ° C. By setting such a temperature, epitaxial growth of high-quality GaN can be performed.

Further, the GaN epitaxial layer can be grown by a hydride vapor phase epitaxy method or an organometallic hydrogen chloride vapor phase epitaxy method.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method for growing a GaN epitaxial layer according to the present invention will be described below in detail with reference to the accompanying drawings. Note that the same reference numerals are used for the same elements, and redundant description will be omitted.

FIG. 1 is a manufacturing process diagram showing the growth method of this embodiment. First, in the step shown in FIG.
The s substrate 10 is set in a reaction vessel of a vapor phase growth apparatus.
The GaAs substrate 10 is made of GaAs (111) A
Either a substrate or a GaAs (111) B substrate may be used.

Referring to FIG. 2, H used in the present embodiment
The vapor phase growth apparatus 50 for the VPE (Hydride Vapor Phase Epitaxy) method will be described. The vapor phase growth apparatus 50 includes a reaction chamber 59 having a first gas introduction port 51, a second gas introduction port 53, a third gas introduction port 55, and an exhaust port 57, and a resistance heating for heating the reaction chamber 59. And a heater 61. Further, a source boat 63 made of Ga metal and a GaAs
A rotation support member 65 that supports the s substrate 10 is provided.

Using such a vapor phase growth apparatus 50, in the step shown in FIG.
On GaN, a buffer layer 20 of GaN (gallium nitride) is grown.

The method of growing the GaN buffer layer 20 will be described in detail.
With the temperature of the substrate 10 kept at about 450 ° C. to about 600 ° C., hydrogen chloride (HC) is supplied through the second gas introduction port 53.
l) is changed to Ga at a partial pressure of 1 × 10 ⁻⁴ atm to ⁴ × 10 ⁻³ atm.
The metal source boat 63 is introduced. By this treatment, Ga metal reacts with hydrogen chloride (HCl) to generate gallium chloride (GaCl).

Next, ammonia (NH ₃ ) is supplied through the first gas introduction port 51 to a partial pressure of 0.05 atm to 0.5 atm.
And the NH ₃ and GaC near the GaAs substrate 10.
and GaN to produce GaN. In addition, hydrogen (H ₂ ) is introduced as a carrier gas into the first gas introduction port 51 and the second gas introduction port 53. Also, only hydrogen (H ₂ ) is introduced into the third gas introduction port 55. By growing GaN under such conditions for about 5 minutes to about 60 minutes, a thickness of about 200 nm is formed on the GaAs substrate 10.
Angstrom to about 2000 Angstrom (× 1
0 ^-10 m) of the GaN buffer layer 20 can be grown in.

As described above, the GaN buffer layer 20
By setting the thickness in the range of 200 angstroms to 2000 angstroms, lattice mismatch between the GaAs substrate 10 and a GaN epitaxial layer, which will be described later, can be reduced, and a favorable epitaxial layer can be obtained.
Further, the growth temperature of the GaN buffer layer 20 is set to 450 ° C. to 6 ° C.
By setting the temperature within the range of 00 ° C., the GaAs substrate 10 and the Ga
A buffer layer capable of alleviating lattice mismatch with the N epitaxial layer

After forming the GaN buffer layer 20 in this manner, the output of the heating temperature of the resistance heater 61 is improved,
From the temperature at which the GaN buffer layer 20 was formed to the temperature at which the next GaN epitaxial layer should be grown, Ga
The temperature of the As substrate 10 is raised. The temperature at which the GaN epitaxial layer should be grown is preferably 950 ° C. or higher.
By growing at such a temperature, good quality GaN
Can be epitaxially grown.

After raising the temperature of the GaAs substrate 10 to a predetermined temperature, the GaN buffer layer 2 is formed in a step shown in FIG.
Then, a GaN epitaxial layer 30 is grown on the substrate. Ga
The N epitaxial layer 30 is grown by the HVPE method using the vapor phase growth apparatus 50 of FIG. Specifically, the temperature of the GaAs substrate 10 is reduced to about 9 by the resistance heater 61.
While maintaining the temperature at 50 ° C. to about 1030 ° C., about 20 μm / h
A GaN epitaxial layer 30 having a thickness of about 20 μm to about 600 μm is grown on the GaN buffer layer 20 at a growth rate of r to about 200 μm / hr.

After the GaN epitaxial layer 30 is grown, the GaAs substrate 10 is removed to remove the single crystal GaN.
A substrate can be obtained. The GaAs substrate 10 can be easily dissolved and removed with aqua regia or the like.

Here, in the present embodiment, G
The temperature is raised from the growth temperature of the aN buffer layer 20 to the temperature at which the GaN epitaxial layer 30 is grown in a short time of 35 minutes or less. For this reason, the reaction between GaAs and a gas such as NH ₃ used for growing GaN,
The decomposition of aAs can be prevented, and the crystal quality of the GaAs substrate 10 is not degraded even in the growth stage of the GaN epitaxial layer 30. Therefore, such GaAs
The GaN epitaxial layer 30 grown on the substrate 10
Good crystal quality.

As described above, by rapidly raising the temperature of the substrate on which the GaN buffer layer is formed, it is possible to prevent the reaction and decomposition of GaAs and grow a good-quality GaN crystal on the GaAs substrate. G at high temperatures
This overturns the common belief that the aAs substrate is deteriorated by being attacked by NH ₃ . After the growth of the epitaxial layer,
The fact that a large-sized GaN substrate can be obtained by dissolving and removing the GaAs substrate 10 opens a new and superior path to the manufacturing technology of the GaN-based device formed on the sapphire substrate, and its industrial value is It is extremely large and can be put to practical use.

In this embodiment, the GaN epitaxial layer 30 is grown by the hydride vapor phase epitaxy method.
It can also be grown by E method; Metal Organic Hydrogen Chloride VPE). In the metalorganic hydrogen chloride vapor phase epitaxy, gallium chloride (GaCl) is produced by reacting trimethylgallium (TMG) with hydrogen chloride (HCl), and GaCl is reacted with NH ₃ to produce GaN. . Even when a method other than the hydride vapor phase epitaxy is used, GaAs may be formed at the epitaxial layer growth stage.
Since the substrate 10 has not reacted or decomposed, GaN
The crystal quality of the epitaxial layer 30 becomes good.

In this embodiment, the GaAs substrate 10
Is raised to around 500 ° C. to form the GaN buffer layer 20, and subsequently to the growth temperature of the GaN epitaxial layer 30 (around 1000 ° C.). Alternatively, a GaAs substrate on which a GaN buffer layer 20 has been grown but which has been cooled to about room temperature is prepared and
raising the temperature to around the temperature at which the aN buffer layer 20 was formed,
Thereafter, the temperature may be raised to a temperature at which the GaN epitaxial layer 30 is to be formed within 35 minutes.

[0029]

Next, the present invention will be described more specifically based on examples.

Example 1 (111) A of GaAs substrate
After a GaN buffer layer having a thickness of 50 nm was formed at 500 ° C. on the surface, the GaAs substrate was heated to 1000 ° C. for 20 minutes. Then, GaN was epitaxially grown on the buffer layer over a period of 2 hours at a speed of 50 μm / hour. When the substrate was cooled and the substrate was observed, it was observed that GaN on the mirror surface was grown on the GaAs substrate. FIG. 3 shows a micrograph of the GaN surface at this time. G
When the aAs substrate was dissolved in aqua regia and the thickness of GaN was measured, it was 100 μm.

[Comparative Example 1] (111) A of GaAs substrate
After forming a GaN buffer layer having a thickness of 50 nm at 500 ° C. on the surface, the GaAs substrate was heated to 1000 ° C. in 50 minutes. Then, GaN was epitaxially grown on the buffer layer over a period of 2 hours at a speed of 50 μm / hour. During the growth of the epitaxial layer, it was observed that the amount of As deposited increased at locations protruding from the electric furnace below the reaction. After growth, the temperature was lowered and the substrate was
The GaAs substrate was almost degraded and ragged.

Example 2 (111) A of GaAs substrate
After forming a GaN buffer layer with a thickness of 50 nm at 550 ° C. on the surface, the correlation between the heating rate (heating time) and the crystal quality of GaN was examined. A correlation was found between the value of the value width and the time required to raise the temperature from 550 ° C. to 1000 ° C. (the difference was 450 ° C.).

FIGS. 4 and 5 show the dependency of the X-ray half-width on the heating rate and the dependency of the X-ray half-width on the heating time, respectively. As shown in FIG. 4, it can be seen that when the heating rate is 12.9 ° C./min or more, the X-ray half width is minimized. still,
The X-ray half width at a heating rate of 12.9 ° C./min is 19.
The X-ray half-width at 0 minutes and when the heating rate is 15 ° C./min is 1
The X-ray half-width at 9.0 minutes and when the temperature was raised at a rate of 16.1 ° C./minute was 19.0 minutes. The fact that the rate of temperature rise is 12.9 ° C./minute or more means that the temperature rise rate is from 550 ° C. to 1000 ° C.
This means that the temperature rise time to 35 ° C. is within 35 minutes.

Further, the present inventors have confirmed through experiments that a remarkable effect can be obtained by increasing the heating rate even when the growth temperature is set to 1000 ° C. or lower. In this experiment, when the GaAs substrate was heated to 950 ° C. for 22 minutes after the GaN buffer layer was formed, the X-ray half-width was 25 minutes, and the mirror planarization rate of the GaN epitaxial layer was 6%.
The crystal quality was relatively good at 6%. On the other hand, after forming the GaN buffer layer, the GaAs
When the temperature of the s substrate was raised, the X-ray half width was 100 minutes, and Ga
The mirroring ratio of the N epitaxial layer was 0%.

As described above, the invention made by the present inventors has been specifically described based on the embodiments. However, the present invention is not limited to the above embodiments.

[0036]

As described above, according to the method of growing a GaN epitaxial layer of the present invention, the temperature is raised from the growth temperature of the GaN buffer layer to the temperature at which the GaN epitaxial layer is grown within a short time of 35 minutes or less. Therefore, the crystal quality of the GaAs substrate does not deteriorate. Therefore, the GaN epitaxial layer grown on such a GaAs substrate has good crystal quality.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram showing a growth process of a GaN epitaxial layer of the present invention.

FIG. 2 is a cross-sectional view showing a vapor phase growth apparatus for growing a GaN buffer layer and a GaN epitaxial layer by a hydride vapor phase epitaxy method.

FIG. 3 is a micrograph showing a surface state of a GaN epitaxial layer obtained by a growth method of the present invention.

FIG. 4 is a graph showing the temperature-rise rate dependence of the X-ray half-width (GaN crystal quality).

FIG. 5 is a graph showing the temperature rise time dependency of the X-ray half-width (crystal quality of GaN).

[Explanation of symbols]

10: GaAs substrate, 20: GaN buffer layer, 30:
GaN epitaxial layer, 59 ... reaction chamber, 61 ...
Resistance heater.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshinao Kumagai 2-41-7, Sachimachi, Fuchu-shi, Tokyo Fuchu 2nd Inn Building 303 (72) Inventor Kikuro Takemoto 1-1-1, Kunyokita, Itami-shi, Hyogo No. Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor Hiroya Kimura 1-1-1, Koyo Kita, Itami City, Hyogo Prefecture Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor Jin Kasai Kitaichi, Kyoyo Itami City, Hyogo Prefecture 1-1 1-1 Sumitomo Electric Industries, Ltd. Itami Works F term (reference) 4G077 AA03 BE15 DB05 DB08 EA02 ED06 EF03 TB03 TB05 TC06 TC13 5F041 AA40 CA40 CA46 CA64 5F045 AA01 AA03 AA04 AB14 AC03 AC12 AD08 AD09 AD10 AD13 AF04 DA53 DP03 5F052 GC04 GC10 HA01 JA07 KA01 KA05 KA06 5F073 CA02 CB02 CB07 DA04 DA05 EA28

Claims (5)

[Claims] A step of growing a GaN buffer layer on a GaAs substrate;
A method for growing a GaN epitaxial layer, comprising: raising a temperature within 5 minutes; and growing a GaN epitaxial layer on the GaN buffer layer. 2. The method according to claim 1, wherein the GaN buffer layer has a thickness of 200 to 200.
2. The method for growing a GaN epitaxial layer according to claim 1, wherein the thickness is in the range of 2000 angstrom. 3. The growth temperature of the GaN buffer layer is 4
The method for growing a GaN epitaxial layer according to claim 1, wherein the temperature is in a range of 50C to 600C. 4. The GaN epitaxial layer has a thickness of 950.
2. The method for growing a GaN epitaxial layer according to claim 1, wherein the method is performed at a temperature of not less than C. 5. The GaN epitaxial layer according to claim 1, wherein the GaN epitaxial layer is grown by a hydride vapor phase epitaxy method or an organometallic hydrogen chloride vapor phase epitaxy method.
A method for growing an epitaxial layer.