JPH08188498A - Epitaxial wafer and its production - Google Patents

Abstract

PURPOSE: To obtain an epitaxial wafer having excellent performance and to provide a method to inexpensively and industrially produce the wafer. CONSTITUTION: The objective wafer is composed of a GaAs substrate having a plane azimuth slightly tilted from a (111)B plane, a buffer layer comprising GaN formed on the plane of the substrate and an epitaxial layer containing GaN or GaInN formed on the buffer layer. The buffer layer and the epitaxial layer are formed by an organic metal chloride vapor phase epitaxy-growing method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epitaxial wafer and a method for manufacturing the same, and more particularly to an epitaxial wafer used for a light emitting device or a high temperature operating semiconductor device having a high luminous efficiency of blue and green and a method for manufacturing the same. It is a thing.

[0002]

2. Description of the Related Art As a high-brightness light emitting diode (LED), for example, red light, aluminum gallium arsenide (AlGaAs) or gallium arsenide phosphide (GaAsP) is used.
A material using such a material has been put to practical use, and a brightness of several candela or more has been realized by a low-cost LED.

On the other hand, for LEDs other than red, for example, green gallium phosphide (GaP), blue silicon carbide (SiC), blue or blue-green gallium indium nitride (GaInN), orange or yellow phosphor is used. Aluminum gallium indium (AlGaInP)
Are being studied. However, Ga
As for the LED using P and SiC, since the material is an indirect transition type semiconductor, a high brightness of a candela class has not been realized yet. Further, with respect to AlGaInP, cost reduction has not been realized because it is necessary to increase the thickness of the cladding layer.

Among these, an example using GaInN, which has been most successful as a blue or blue-green light emitting diode, is described in Nikkei Science October 1994 p. 44
(Hereinafter referred to as “Reference 1”) and the like.

FIG. 4 is a sectional view showing the structure of an example of an epitaxial wafer used for such a conventional blue light emitting diode.

Referring to FIG. 4, this epitaxial wafer includes a sapphire substrate 11, a gallium nitride (GaN) buffer layer 12 formed on substrate 11, and a hexagonal GaN layer formed on GaN buffer layer 12. It is composed of an epitaxial layer 13. In this epitaxial wafer, the GaN buffer layer 12 is provided to reduce strain due to the difference in lattice constant between the sapphire substrate 11 and the GaN epitaxial layer 13.

FIG. 5 is a sectional view showing the structure of a GaN-based blue light emitting device using the epitaxial wafer shown in FIG.

With reference to FIG. 5, this blue light emitting device comprises a cladding layer 14 and an epitaxial wafer on the epitaxial wafer shown in FIG.
The light emitting layer 15, the cladding layer 16 and the GaN epitaxial layer 17 are sequentially formed, and the GaN epitaxial layer 1
Ohmic electrodes 18 and 19 are formed on the electrodes 3 and 17, respectively. Further, in this blue light emitting element,
Hexagonal aluminum gallium nitride (AlGaN) is used for the cladding layers 14 and 16, hexagonal GaInN is used for the light emitting layer 15, and the same hexagonal sapphire is used for the substrate 11.

Referring to FIGS. 4 and 5, since this epitaxial wafer uses insulating sapphire as substrate 11 as described above, photolithography is performed when forming electrodes by forming electrodes. Is required twice or more, and the nitride layer needs to be etched by reactive ion etching, which requires complicated steps. Further, since sapphire has high hardness, it is difficult to handle. Furthermore, this sapphire
Since the cleavage cannot be performed, there is a problem in the application of the light emitting element that it cannot be applied to the laser diode having the cleavage end face as the optical resonator.

Further, in order to grow hexagonal AlGaN or GaInN having good crystallinity on a sapphire substrate, it is necessary to grow at high temperature.
It is necessary to grow at a temperature of 0 ° C. or higher, and even GaInN at a temperature of 800 ° C. or higher. However, in the case of Ga _{1 -X} In _X N (0 <X <1) used for the light emitting layer, since the sticking coefficient of In is small, at a high temperature of 800 ° C. or higher, X
It is difficult to form a GaInN layer having an In composition of ≧ 0.3. Therefore, X <0.3, and the energy of the band width becomes ultraviolet or purple. Therefore, in order to obtain a desired blue or blue-green color, it is necessary to introduce an emission center such as zinc (Zn) that forms a deep level. However, light emission from such a light-emitting layer in which a light-emitting center is introduced has a wide spectrum and is poor in purity, and has an appropriate light-emitting element performance when considered for applications such as a full-color display. It is hard to say that

Therefore, it has been attempted to use conductive GaAs as a substrate in place of sapphire which has such drawbacks. However, if the substrate is GaA
If s was changed to s, under the same conditions as when the sapphire substrate was used, it was not possible to obtain an epitaxial wafer comparable to that when the sapphire substrate was used.

Therefore, various studies have been conducted on the production of epitaxial wafers using GaAs as a substrate.

Among these, for example, Appl. Phys Le
tt. 59 (1991) p. 1058 (hereinafter referred to as “reference 2”)
), A GS-MBE method (gas source molecular beam epitaxy growth method) is used to obtain Ga that is easily conductive.
It is disclosed to grow a GaN epitaxial layer on an As substrate. In this GS-MBE method, triethylgallium (TEGa) vaporized as a group III raw material is plasma-treated as a group V raw material while heating only a substrate in the reaction chamber by resistance heating in a reaction chamber kept in an ultrahigh vacuum. This is a method of introducing vaporized ammonia gas or nitrogen gas to vapor-phase grow a GaN epitaxial layer on the substrate. In this case, cubic GaN is heteroepitaxially grown on the (100) plane of GaAs and hexagonal GaN is heteroepitaxially grown on the (111) plane of GaAs.

Further, Applied Physics 63 (1994) p. 15
6 (hereinafter referred to as “reference 3”) and Jpn. J. Appl. Ph.
ys. 33 (1994) p. 3415 (hereinafter referred to as "reference 4")
), The OMVPE method (metalorganic vapor phase epitaxy method) is used to form GaN or Ga on the GaAs substrate.
The growth of InN epitaxial layers is disclosed. In this OMVPE method, a first gas containing trimethylgallium (TMGa) or triethylgallium (TEGa) as a group III raw material and ammonia (NH ₃ ) as a group V raw material are used while heating only the substrate in the reaction chamber by high frequency heating. Is introduced into the reaction chamber and a GaN epitaxial layer is vapor-grown on the substrate. In this case, (100) of GaAs substrate
A cubic GaN epitaxial layer grows on both the plane and the (111) plane.

[0015]

However, as shown in, for example, Document 2, when the GS-MBE method is used, the growth rate of the GaN epitaxial layer is extremely slow,
It is difficult to set it to 0.15 μm / hour or more. Therefore, the production of epitaxial wafers by this method is
There is a problem that the cost cannot be reduced and it is not suitable for industrialization. Further, although it has been attempted to improve the growth rate by plasma-exciting and decomposing ammonia as a V group raw material that is the rate-determining factor of the growth reaction, efficient decomposition has not been achieved, and a sufficient growth rate is not achieved. Not obtained.

On the other hand, as shown in, for example, Documents 3 to 4,
Even when the OMVPE method is used, it is difficult to obtain a growth rate of 0.4 μm / hour or more, and there is a problem that it is not suitable for industrialization. Further, when the OMVPE method is used, ridge-shaped irregularities appear on the surface of the obtained epitaxial layer, and it is difficult to form an epitaxial layer having a good surface morphology.

Further, since the OMVPE method is a so-called cold wall that heats only the substrate in the reaction chamber, ammonia is not sufficiently decomposed. Therefore, it is necessary to increase the supply amount of ammonia to make up for the portion that is difficult to decompose, and to supply a high V / III ratio (V group raw material and II
(Compared to Group I raw materials).

For example, Appl Phys. Lett. 64 (199
4) p. 1687, GaN on sapphire substrate
The V / III ratio during growth was ˜6.0 × 10 ³ , and Ga
It is calculated from the value of the amount of raw material introduced during growth that the V / III ratio during growth of InN is ˜1.1 × 10 ⁴ . As described above, according to the OMVPE method, there is a problem that an epitaxial wafer cannot be manufactured at low cost because it consumes a huge amount of raw material.

Further, according to the OMVPE method, epitaxial growth is carried out at a high temperature of 800 ° C. or higher in order to promote decomposition of ammonia as a group V raw material. However, when the growth rate becomes high as described above, the high In composition is obtained. There is also a problem that it becomes difficult to form the GaInN layer.

An object of the present invention is to solve the above-mentioned problems and to provide a high-performance epitaxial wafer and a method of manufacturing the epitaxial wafer industrially at low cost.

[0021]

An epitaxial wafer according to a first aspect of the present invention comprises a GaAs substrate having a plane whose plane orientation is slightly inclined from the (111) B plane, and GaN formed on the plane of the substrate. And a epitaxial layer containing GaN or GaInN formed on the buffer layer.

In the invention of claim 1, it is preferable that the plane whose plane orientation is slightly inclined from the (111) B plane is (11).
1) Face turned off in the range of 0 ° to 2 ° in the closest <100> direction from the B face, or turned off in the range of 0 ° to 2 ° in the <011> direction closest to the (111) B face. It is good to let it be the surface.

In the method for producing an epitaxial wafer according to the third aspect of the present invention, the GaAs substrate having a plane whose surface orientation is slightly inclined from the (111) B plane is chlorinated while externally heating the entire reaction chamber. A first gas containing an organometallic material containing hydrogen and gallium and a second gas containing ammonia
Gas is introduced into the reaction chamber and vapor phase growth is performed on the substrate placed in the reaction chamber, and a step of forming a buffer layer made of GaN, and heating the entire reaction chamber from the outside onto the buffer layer. However, a first gas containing (1) a gas containing an organometallic raw material containing hydrogen chloride and gallium or (2) a gas containing an organometallic raw material containing hydrogen chloride, gallium and an organometallic raw material containing indium and a first gas containing ammonia The gas of No. 2 is introduced into the reaction chamber, and vapor growth is performed on the substrate placed in the reaction chamber.
Forming an epitaxial layer containing N or GaInN.

As the organic metal raw material containing gallium, for example, trimethylgallium (TMGa), triethylgallium (TEGa) or the like is used. Further, as the organic metal raw material containing indium, for example, trimethylindium (TMIn) or the like is used.

In the third aspect of the invention, preferably, the plane whose plane orientation is slightly inclined from the (111) B plane is (11
1) Face turned off in the range of 0 ° to 2 ° in the closest <100> direction from the B face, or turned off in the range of 0 ° to 2 ° in the <011> direction closest to the (111) B face. It is good to let it be the surface.

[0026]

The epitaxial wafer according to the present invention has a Ga
On a surface slightly inclined from the (111) B plane of the As substrate, specifically, a surface turned off in the range of 0 ° to 2 ° in the closest <100> direction from the (111) B plane, or ( 111) B
An epitaxial layer is formed on the surface turned off in the range of 0 ° to 2 ° in the <011> direction closest to the surface.

Therefore, a ridge does not appear on the surface of the epitaxial layer as in the conventional case, an epitaxial wafer having a good surface morphology and a very flat surface can be obtained.

Further, according to the method of manufacturing an epitaxial wafer according to the present invention, in forming the epitaxial layer, while heating the entire reaction chamber from the outside, (1) a gas containing an organometallic raw material containing hydrogen chloride and gallium or (2) ) On a substrate placed in the reaction chamber by introducing into the reaction chamber a first gas consisting of a gas containing an organometallic raw material containing hydrogen chloride, gallium and an organometallic raw material containing indium and a second gas containing ammonia. Vapor growth method (below,
"Organic metal chloride vapor phase epitaxy method")
Is used. This organometallic chloride vapor phase epitaxy growth method has a high growth rate and is capable of obtaining a steep hetero interface.

Further, according to this organometallic chloride vapor phase epitaxy growth method, the epitaxial layer can be grown at a lower temperature than before. Therefore, Ga _1-X In
_In the formation of the XN epitaxial layer, I with X ≧ 0.3
It becomes possible to form a GaInN epitaxial layer having an n composition. As a result, in the entire range of 0 ≦ X ≦ 1, Ga
It becomes possible to form a _1-X In _X N epitaxial layer. Since the band energy of GaInN in this region covers the range of orange, yellow, green, blue, and purple, the band edge emission described above can be performed without introducing a deep emission center level such as Zn as in the conventional case. An LED capable of emitting light of any color can be manufactured.

[0030]

【Example】

(Embodiment 1) FIG. 1 is a diagram showing a schematic structure of a vapor phase growth apparatus used for manufacturing an epitaxial wafer using the organometallic chloride vapor phase epitaxy method according to the present invention. Referring to FIG. 1, this apparatus heats a reaction chamber 54 having a first gas introduction port 51, a second gas introduction port 52, and an exhaust port 53, and the inside of the reaction chamber 54 from the outside thereof. And a resistance heater 55 for heating.

By using the apparatus configured as described above, Ga
A GaN epitaxial layer was grown on an As substrate and an epitaxial wafer was prepared as follows. The substrate is a GaAs (100) plane substrate, (1
Four types were used: an 11) B-side substrate, a (111) B-plane <100> direction 1 ° off substrate, and a (111) B-side <011> direction 2 ° off substrate.

Referring to FIG. 1, first, each substrate 1 of gallium arsenide GaAs pretreated with a normal etching solution of H ₂ SO ₄ system was placed in a reaction chamber 54 made of quartz.

Next, the inside of the chamber is externally heated by the resistance heater 55 and the substrate 1 is maintained at 500 ° C., and trimethylgallium (TMGa) and a group III source material are added from the first gas inlet 51. Hydrogen chloride (H
Cl) partial pressure of 8 × 10 ^-4 atm and 8 × 10 ^-4 a, respectively.
At the same time, ammonia gas (NH ₃ ) as a group V raw material is introduced from the second gas inlet 52 at a partial pressure of 1.6 × 1.
It was introduced at 0 ^-1 atm. Under these conditions, epitaxial growth was performed for 15 minutes to form a GaN buffer layer having a thickness of 300Å. By interposing this buffer layer, the crystallinity of the epitaxial growth layer formed thereon can be significantly improved.

Next, the temperature of the substrate 1 on which the GaN buffer layer is thus formed is set to 75 by the resistance heater 55.
After raising the temperature in the range of 0 ° C to 800 ° C, TMGa, HC
l and NH ₃ partial pressures of 8 × 10 ⁻⁴ atm and 8 × 1 respectively
60 under the condition of 0 ^-4 atm and 1.6 × 10 ^-1 atm
It was epitaxially grown for a minute.

As a result, a thickness of 2 is formed on the GaN buffer layer.
A μm mirror-like GaN epitaxial layer was formed.

With respect to the four types of epitaxial wafers thus obtained, the characteristics of the GaN epitaxial layer formed were evaluated as follows.

First, the X-ray diffraction pattern of the GaN epitaxial layer was analyzed. As a result, all four types of single-crystal GaN were well oriented with respect to the direction perpendicular to the substrate surface.
It was found that the epitaxial layer had grown.

Next, in order to investigate the surface flatness of the GaN epitaxial layer, which is one of the important characteristics in device manufacturing, each epitaxial wafer sample is cleaved, and the SEM ( It was observed with a scanning electron microscope.

FIG. 2 shows the GaAs (111) B plane <100.
It is the photograph which observed the crystal structure of the GaN epitaxial layer at the time of using a 1-degree off substrate> by SEM from the cleavage plane. It can be seen from FIG. 2 that a very flat GaN epitaxial layer is formed on the GaN buffer layer formed on the GaAs substrate.

Further, FIG. 3 shows this GaAs (111) B.
GaN when using a 1 ° off substrate in the <100> plane
It is a figure which shows the measurement result of the surface unevenness of an epitaxial layer. In FIG. 3, the horizontal axis represents the horizontal position (μm), and the vertical axis represents the surface unevenness (Å). The surface unevenness is the difference between the highest point of the convex portion and the lowest point of the concave portion.

Further, GaAs (111) B plane <011>
It was confirmed that a very flat GaN epitaxial layer was also formed when the 2 ° off substrate was used.

Further, it was found that when the growth temperature is in the range of 750 ° C. to 800 ° C., a GaN epitaxial layer having a flat surface is formed in each case.

(Example 2) As in Example 1, using the apparatus shown in FIG. 1, a GaInN epitaxial layer was grown on a GaAs substrate, and an epitaxial wafer was prepared as follows. The substrate is a (100) plane substrate of GaAs, a (111) B plane substrate, or a (111) B plane substrate.
Plane <100> Direction 1 ° Off Substrate and (111) B Side <
Four kinds of 011> direction 2 ° off substrate were used.

Referring to FIG. 1, similarly to the first embodiment, first, in a reaction chamber 54 made of quartz, gallium arsenide Ga pretreated with a normal H ₂ SO ₄ type etching solution is used.
Each substrate 1 of As was installed.

Next, the inside of the chamber is externally heated by the resistance heater 55 and the substrate 1 is kept at 500 ° C., and trimethylgallium (TMGa) and a group III raw material are added from the first gas inlet 51. Hydrogen chloride (H
Cl) partial pressure of 8 × 10 ^-4 atm and 8 × 10 ^-4 a, respectively.
At the same time, ammonia gas (NH ₃ ) as a group V raw material is introduced from the second gas inlet 52 at a partial pressure of 1.6 × 1.
It was introduced at 0 ^-1 atm. Under these conditions, epitaxial growth was performed for 15 minutes to form a GaN buffer layer having a thickness of 300Å.

Next, the temperature of the substrate 1 on which the GaN buffer layer is thus formed is set to 60 by the resistance heater 55.
After raising the temperature to 0 ° C., the partial pressures of TMGa, TMIn (trimethylindium), HCl and NH ₃ are each 8 × 1.
0 ^-5 atm, 7.2 x 10 ^-4 atm, 8 x 10 ^-4 at
Under conditions of m, 1.6 × 10 ⁻¹ atm, epitaxial growth was performed for 60 minutes.

As a result, a mirror-like GaInN epitaxial layer having a thickness of 0.5 μm was formed on the GaN buffer layer.

On the four types of epitaxial wafers thus formed, it was found that a single crystal GaInN epitaxial layer which was well oriented with respect to the direction perpendicular to the substrate surface was grown. It became clear from the analysis of. The X of the In structure was about 0.2.

Furthermore, on the (111) B plane, (111) B
Face <100> direction 1 ° off, (111) B face <011
As for the three types of epitaxial wafers on the direction of> 2 ° off, the GaI having a very flat surface similar to that in Example 1 was used.
It was confirmed that the nN epitaxial layer was formed.

[0050]

As described above, according to the present invention, an epitaxial layer having a good surface morphology can be formed.

Further, the heteroepitaxial wafer according to the present invention can be obtained with high purity in electrical characteristics. Therefore, it is applied to the manufacture of nitride semiconductor light emitting devices such as LEDs and high performance nitride semiconductor devices capable of high temperature operation.

Further, according to the present invention, an epitaxial wafer used for high-luminance, purple, blue, green, yellow, and orange nitride semiconductor LEDs can be obtained by a simple and low-cost process. Since each of these LEDs has a narrow spectrum spread, it can be applied to a full-color LED display having excellent color resolution.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a vapor phase growth apparatus used for manufacturing an epitaxial wafer using a metal organic chloride vapor phase epitaxy method according to the present invention.

FIG. 2 is a photograph of the crystal structure of an example of an epitaxial wafer according to the present invention, observed by SEM from the cleavage plane.

FIG. 3 is a diagram showing a measurement result of surface unevenness of a GaN epitaxial layer which is an example of an epitaxial wafer manufactured according to the present invention.

FIG. 4 is a cross-sectional view showing a structure of an example of a conventional epitaxial wafer.

5 is a cross-sectional view showing the structure of a blue light emitting device using the epitaxial wafer shown in FIG.

[Explanation of symbols]

 1 GaAs Substrate 51 First Gas Inlet 52 Second Gas Inlet 53 Exhaust 54 Reaction Chamber 55 Resistance Heater

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01S 3/18 (72) Inventor Sekisui 3-21-12 Nanyodai, Hachioji-shi, Tokyo (72) Invention纈 纈 meihaku 2-41-13 Sachimachi, Fuchu-shi, Tokyo

Claims (4)

[Claims] 1. A GaAs substrate having a plane whose plane orientation is slightly inclined from the (111) B plane, a buffer layer made of GaN formed on the plane of the substrate, and a GaAs substrate formed on the buffer layer. GaN or GaInN
And an epitaxial layer including. 2. The surface whose plane orientation is slightly inclined from the (111) B surface is a surface turned off in the range of 0 ° to 2 ° in the closest <100> direction from the (111) B surface, or (11
1) The epitaxial wafer according to claim 1, which is a surface turned off in the range of 0 ° to 2 ° in the closest <011> direction from the B surface. 3. A GaAs substrate having a plane orientation slightly inclined from the (111) B plane and containing an organometallic raw material containing hydrogen chloride and gallium while heating the entire reaction chamber from the outside. Forming a buffer layer made of GaN by a method of introducing the first gas and a second gas containing ammonia into the reaction chamber and performing vapor phase growth on a substrate installed in the reaction chamber; While heating the entire reaction chamber from the outside, from (1) a gas containing an organometallic raw material containing hydrogen chloride and gallium or (2) a gas containing an organometallic raw material containing hydrogen chloride, gallium and an indium GaN or GaI by a method of introducing the first gas and the second gas containing ammonia into the reaction chamber and performing vapor phase growth on the substrate installed in the reaction chamber. And a step of forming an epitaxial layer containing an N, method for manufacturing an epitaxial wafer. 4. The plane in which the plane orientation is slightly tilted from the (111) B plane is a plane turned off in the range of 0 ° to 2 ° in the <100> direction closest to the (111) B plane, or (11
1) The method for producing an epitaxial wafer according to claim 3, wherein the surface is turned off in the range of 0 ° to 2 ° in the closest <011> direction from the B surface.