JPH0586646B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a -V group compound semiconductor _Al
The present invention relates to a method for growing thin films of Ga _1-x N (0≦x≦1) and InN.

[Prior art]

Conventionally, in order to grow a GaN film, which is a -V group compound semiconductor, the main method was to use a sapphire C-plane as a substrate, introduce GaCl ₃ and NH ₃ into a vacuum container, and then heat the halide gas to be thermally decomposed on the substrate. Phase growth methods have been used. In this vapor phase growth method, in addition to the fact that growth deviates from thermal equilibrium, the grown GaN film usually has nitrogen vacancies due to the difference in lattice constant, or lattice mismatch, between the sapphire substrate and the GaN film. The drawback was that it contained many dots and had poor crystallinity. Another disadvantage was that the grown GaN film had a low resistance due to the influence of the nitrogen vacancies, and in order to obtain a high resistance GaN film, a large amount of acceptor dopant such as Zn or Mg had to be added. In addition to this, there was also the problem that GaCl ₃ and NH ₃ reacted locally, making it impossible to form a uniform film.

Metal-organic vapor phase epitaxy, in which thin films are grown using trimethyl gallium (TMG)-NH ₃ -N ₂ (or H ₂ ) system on saphire C-plane substrates, provides good film uniformity, but the lattice mismatch problem is not resolved,
The grown GaN film had the drawback of containing many nitrogen vacancies.

On the other hand, for the growth of Al _x Ga _1-x N (0<x<1) thin films, vapor phase growth and reactive MBE have been mainly used using sapphire C-plane substrates. In halide-based and organometallic vapor phase epitaxy, the above-mentioned GaN
As in the case of the film, the grown Al _x Ga _1-x N (0<x
1) The film had a drawback in that it had many nitrogen vacancies due to lattice mismatch.

Even in the reactive MBE method using the Al-Ga-NH ₃ system, the film grown on the Saphire C surface has the drawback that it contains many nitrogen vacancies due to lattice mismatch.

The InN thin film is mainly grown by an InCl ₃ -NH ₃ based vapor phase growth method using a sapphire C-plane substrate.
In this case as well, in addition to the growth under thermal non-equilibrium conditions, there was a drawback that a large number of nitrogen vacancies were included due to the influence of lattice mismatch, as in the above two examples.

〔the purpose〕

Therefore, the purpose of the present invention is to improve lattice matching to produce high-quality carbon fibers with fewer nitrogen vacancies.
An object of _the present invention is to provide a method for growing a compound semiconductor thin film that can grow an Al _{x Ga 1-x} N (0≦x≦1) or InN epitaxial film.

[Structure of the invention]

In order to achieve such an object, the present invention uses organic metal-based Al _x Ga _1-x N (0≦x≦1) or
When growing an InN epitaxial film,
A buffer layer having the same composition as the epitaxial film is provided between the substrate and the epitaxial film by high frequency sputtering.

That is, the present invention uses an optically polished sapphire C-plane substrate or an optically polished glass conductive substrate with a metal vapor-deposited, targets at least one of metal aluminum, metal gallium, and metal indium, and connects the target and the substrate. By applying a DC bias between the
Al _x Ga _1-x N (0≦x≦
1) Alternatively, InN is deposited as a buffer layer on the substrate, and then the substrate with the buffer layer deposited is placed in a reduced pressure container, and the substrate is exposed to NH _{3 .}
Heating in an atmosphere containing a gas and supplying a group organic metal, decomposing the group organic metal on the heated substrate and vapor-growing a nitride film thereof on the buffer layer. Al _x Ga _1-x N (0x1) having the same composition as the buffer layer or
It is characterized by epitaxial growth of InN.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows an example of the film structure of a thin film grown according to the present invention when a saphire C-plane is used as a substrate. Here, 1 is an optically polished sapphire C-plane substrate, and 2 is an Al _x Ga _1-x N (0
≦x≦1) or InN buffer layer 3 is Al _x Ga _1-x N (0≦x≦
1) or an epitaxial layer of InN.

FIG. 2 shows an example of the structure of a thin film grown according to the present invention when a conductive substrate is used. here,
4 is an optically polished glass substrate, 5 is a metal film vacuum-deposited on this glass substrate 4, and 2 is a buffer layer of Al _x Ga _1-X N (0≦x≦1) or InN formed on the metal film 5. , 3 has the same composition as this buffer layer 2.
It is an epitaxial layer of Al _x Ga _1-x N (0≦x≦1) or InN.

Specific examples of the growth method for each composition according to the present invention will be described in detail below.

(Example 1) GaN on Saffire C-plane substrate
Growth of Film (Structure shown in FIG. 1) First, a GaN buffer layer 2 was formed to a thickness of 1000 Å to 7000 Å on an optically polished sapphire C-plane substrate 1 by high frequency sputtering with a DC bias applied. When forming the GaN buffer layer 2 by the high-frequency sputtering method, a parallel plate type device is usually used, and the target is high-purity metallic gallium (Ga, purity 6N to 6N) housed in a stainless steel container.
7N), and placed it on the cathode, placed the Sapphire C-plane substrate 1 on the anode, and
A DC bias is applied to the cathode side using a mixed gas with N ₂ as a sputter gas. In this example, the sputtering gas pressure is set at 3 to 5×10 ^-2 Torr (mixture ratio Ar:N ₂ =3:
7), the sputtering power is 30~50W, the substrate temperature is 300~450℃, and the DC bias voltage is 0~50W.
-100V. Under these growth conditions, a C-axis oriented GaN buffer layer was formed on the C-plane of Saphire.

As the high frequency sputtering device, in addition to this parallel plate type, it is also possible to use a concentric hemispherical type or a magnetron type high frequency sputtering device.

Next, a GaN epitaxial layer 3 is formed on the GaN buffer layer 2 by metal organic vapor phase epitaxy.
The structure shown in Figure 1 was obtained by growing to a thickness of ~10 μm. Here, trimethylgallium TMG was used as the organic metal, and the GaN epitaxial layer 3 was grown using ammonia NH ₃ gas and nitrogen N ₂ carrier gas. More specifically, the substrate 1 is heated to 800 to 1000°C by induction heating, the carrier gas N ₂ is 2 l/min, and the NH ₃ is 500 to 750 cc/min.
And so. Then, TMG was bubbled with carrier gas N ₂ at 20 cc/min at a temperature of -12°C, and the pressure in the reaction tube was reduced to about 0.1 atm to produce C-axis oriented GaN.
Epitaxial layer 3 was grown.

In this way, the buffer layer 2 was provided and grown.
The carrier concentration of GaN epitaxial film is 10 ¹⁸ cm ^-
3. The resistivity is 10 ^-1 Ωcm, which is one to two orders of magnitude lower in carrier concentration than the case without buffer layer 2.
An epitaxial film with resistivity about two orders of magnitude higher and fewer nitrogen vacancies was obtained.

Comparative examples of photoluminescence at room temperature are shown in FIGS. 3 and 4 for a GaN epitaxial film without a buffer layer and a GaN epitaxial film provided with a buffer layer. As can be seen from these Figures 3 and 4, the luminescence intensity of the GaN film with the buffer layer is increased (the intensity ratio of peak A of photoluminescence near the wavelength of 420 nm is (in the case of Figure 3) : (in the case of Figure 4) = 1:13). This is because the number of nitrogen vacancies is reduced, the crystallinity is improved, and the number of non-luminescent centers is reduced. As you can see from this example,
By providing the GaN buffer layer 2, GaN
The quality of epitaxial films is improved.

(Example 2) Growth of a GaN film on a conductive substrate (Structure shown in FIG. 2) First, on a glass substrate 4 made of optically polished quartz glass or Corning 7059 (trade name) glass,
Chromium (Cr), nickel (Ni), molybdenum (Mo),
Metals such as gold (Au) and platinum (Pt) with a thickness of 1000 to 2000Å
The conductive film 5 was obtained by vapor deposition to a thickness of . This conductive film 5
On top of that, GaN was applied under the same conditions as described in Example 1.
A buffer layer 2 was formed. Next, a GaN epitaxial layer 3 was grown on this buffer layer 2 by organometallic vapor phase epitaxy under the same conditions as described in Example 1.

(Example 3) Al _X on Saffire C-plane substrate
Growth of Ga _1-X N (0<x≦1) film (configuration shown in Figure 1) First, Al _x Ga _1-X N (0
<x≦1) Buffer layer 2 was formed to a thickness of 1000 to 7000 Å. The target used was Al pieces arranged on Ga. For example, if x=0.1, Ga
The area of the Al piece was set to 1/10 of the Ga surface area, with the sputtering rate of Al and Al being almost the same. Other growth conditions are
C-axis oriented Al _X as in Example 1
A Ga _1-x N (0<x≦1) buffer layer 2 was formed on a sapphire C-plane substrate 1 . Next, by metalorganic vapor phase epitaxy, _Al
A Ga _1-x N (0<x≦1) epitaxial layer 3 was grown on the buffer layer 2 to a thickness of 1 to 10 μm.
Trimethylaluminum (TMA) was used as the organic metal for Al. The flow rate of TMA was controlled by the bubbling amount of carrier gas N ₂ according to the composition ratio. For example, at x=0.1, the TMA flow rate and
The ratio with the TMG flow rate was set to 1:9. The growth conditions for other organometallic vapor phase epitaxy methods were the same as in Example 1, and a C-axis oriented Al _x Ga _1-x N (0<x≦1) epitaxial layer 3 was grown.

(Example 4) Al _x Ga _1-x N(0
Growth of <x≦1) (Structure shown in FIG. 2) First, in the same process as in Example 2, a conductive film 5 was deposited on a glass substrate 4 to form a conductive substrate. Next, under the same growth conditions as described in Example 3 above, an Al _x Ga _1-x N (0<x≦1) buffer layer 2 and an Al _x Ga _1-x N (0<x1) epitaxial layer 3
grew.

(Example 5) Growth of an InN film on a sapphire C-plane substrate (configuration shown in Fig. 1) First, on an optically polished sapphire C-plane substrate 1, a high-frequency sputtering method was applied using a DC bias.
InN buffer layer 2 was formed to a thickness of 1000 to 7000 Å. When forming the InN layer 2 by high frequency sputtering, In (purity 6N) contained in a stainless steel container was used as a target. Here, set the substrate temperature to
200-400℃, sputtering gas pressure (mixture ratio Ar:N ₂ =
3:7) at 2 to 8 x 10 ^-2 Torr, sputter power to 20 to 40 W, and DC bias voltage to -100 to -150 V.
The C-axis oriented InN layer 2 was formed by setting the following conditions.

Next, an InN epitaxial layer 3 was grown on the buffer layer 2 by metal organic vapor phase epitaxy. Trimethylindium (TMI) was used as the organic metal, NH ₃ was used as the nitrogen source, and N ₂ was used as the carrier gas. TMI flow rate 10~
50cc/min (bubbling amount of carrier gas _N2 ), _NH3 at 100 to 700cc/min, carrier gas _N2
The C-axis oriented InN epitaxial layer 3 was grown under conditions such as 1 to 2 l/min, a substrate temperature of 500 to 700°C, and a reduced pressure of 0.1 atm in the reaction tube.

(Example 6) Growth of InN film on a conductive substrate (Structure shown in Figure 2) First, a conductive film 5 was deposited on a glass substrate 4 in the same process as in Example 2 to form a conductive substrate. .

Next, the InN buffer layer 2 and then the InN epitaxial layer 3 were grown under the same growth conditions as described in Example 5 above.

In the six embodiments described above, the buffer layer 2 and the epitaxial layer 3 have the same composition, but the buffer layer 2 and the epitaxial layer 3 may have different compositions, for example, an AlN buffer layer. Even in the case of a GaN epitaxial layer on top of the GaN layer, the lattice matching is better than when no buffer layer is used, and the thin film growth according to the present invention includes such a case.

〔effect〕

As explained above, in the present invention _, it is possible to grow a high-quality _Al Compared to the growth method, this method has the advantage that when producing an NIS device, the amount of doping for producing an insulating layer can be reduced, and that a high-luminance light-emitting device can be produced. This advantage is particularly advantageous when manufacturing blue light emitting devices in GaN.

In addition, in the present invention, instead of using halide vapor phase epitaxy, which causes a problem of local reactions between GaCl and NH ₃ , we use organometallic vapor phase epitaxy, which does not cause local reactions. Since the matching is good, it also has the advantage that an epitaxial film with excellent uniformity can be obtained.

In addition, the method of the present invention uses the highly popular high-frequency sputtering method in combination with the organometallic vapor phase epitaxy method, which has good uniformity and a fast growth rate.
It also has the advantage of being easy to industrialize and reduce costs.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a configuration example in which an Al _x Ga _1-x N (0≦x≦1) or InN epitaxial film is grown using a sapphire C-plane substrate according to the present invention;
FIG. 2 shows a method using a conductive substrate according to the present invention.
A cross-sectional view showing an example of a structure in which an Al _{x Ga 1-x} N (0≦x≦1) or InN epitaxial film is grown.
Figure 4 shows a characteristic curve of photoluminescence at room temperature when a GaN epitaxial film is grown, and a GaN buffer layer is provided on the sapphire C surface according to the present invention, and a GaN epitaxial film is grown on it. FIG. 3 is a characteristic curve diagram of photoluminescence at room temperature in the case of FIG. 1...Saphire C-plane substrate, 2...Al _X Ga _1-X
N (0≦x≦1) or InN buffer layer, 3...
Al _x Ga _1-x N (0≦x≦1) or InN epitaxial layer, 4... glass substrate, 5... evaporated metal film.

Claims (1)

[Claims] 1. Using an optically polished sapphire C-plane substrate or an optically polished glass conductive substrate with metal vapor-deposited, at least one of metal aluminum, metal gallium, and metal indium is used as a target, and between the target and the substrate, By applying a DC bias and using a high frequency sputtering method in an atmosphere containing nitrogen gas, a -V group compound semiconductor, Al _x Ga _1-x N (0≦x≦1) or InN, is formed as a buffer layer on the substrate. Then, the substrate with the buffer layer deposited thereon is placed in a container under reduced pressure, the substrate is heated in an atmosphere containing NH ₃ gas, and the organic metal of the group is supplied. An organic metal of the above group is decomposed and a nitride film thereof is grown in a vapor phase on a heated substrate, and _AlX having the same composition as that of the buffer layer is formed on the buffer layer.
A method for growing a compound semiconductor thin film, which comprises epitaxially growing Ga _1-x N (0x1) or InN.