JPH1174203A - Method and device for growing nitride iii-v compound semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for growing a nitride III-V compound semiconductor which enables efficient growth of a nitride-based III-V compound semiconductor of high quality. SOLUTION: The pressure inside a reaction tube 1 of an MOCVD device is set at not less than 1.1 atm., particularly not less than 1.1 atm. and not more than 2 atm., preferably 1.2-1.8 atm., and a nitride-based III-V compound semiconductor, for example, GaN, InGaN or the like is grown. The reaction tube 1 is made of quartz glass so as to obtain sufficient strength for withstanding the difference between inner and outer pressures. The surface of a substrate 3 on which the nitride-based III-V compound semiconductor may face upward or downward.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
A method and apparatus for growing a group V compound semiconductor,
In particular, nitride-based III-
The present invention relates to a method and an apparatus for growing a group V compound semiconductor.

[0002]

2. Description of the Related Art A nitride-based III-V compound semiconductor represented by gallium nitride (GaN) (hereinafter also referred to as a "GaN-based semiconductor") emits light that can emit light in a range from green to blue and even ultraviolet rays. It is promising as a material for devices, high-frequency electronic devices, and environmentally-resistant electronic devices. Especially,
Light-emitting diode (LED) using this GaN-based semiconductor
Since the commercialization of GaN-based semiconductors, GaN-based semiconductors have attracted great attention. The realization of a semiconductor laser using this GaN-based semiconductor has also been reported, and applications such as light sources for optical disk devices are expected.

When a light emitting device or an electronic device is manufactured from this GaN-based semiconductor, it is necessary to grow a GaN-based semiconductor in multiple layers on a sapphire substrate, a SiC substrate, or the like. As a method for growing the GaN-based semiconductor, there are a metal organic chemical vapor deposition (MOCVD) method, a molecular beam epitaxy (MBE) method, and the like. Of these methods, the MOCVD method does not require a high vacuum, and is therefore practically advantageous. Yes, it is often used.

Conventionally, when a GaN-based semiconductor is grown by the MOCVD method, the inside of the reaction tube of the MOCVD apparatus is set at normal pressure (1 atm) or reduced pressure (less than 1 atm).
Depending on the GaN-based semiconductor to be grown, gallium (G
a), a raw material such as aluminum (Al) or indium (In) is supplied into the reaction tube together with a carrier gas, and at the same time, a nitrogen raw material represented by ammonia (NH ₃ ) is supplied into the reaction tube. A GaN-based semiconductor was grown on a substrate placed in a tube.

[0005]

SUMMARY OF THE INVENTION However, GaN
Nitrogen is likely to evaporate from the GaN-based semiconductor film during growth due to the high saturated vapor pressure of the system-based semiconductor and the low efficiency of releasing nitrogen atoms by decomposition of a nitrogen source such as ammonia. As a result, the obtained GaN-based semiconductor film becomes deficient in nitrogen, and the film quality is greatly impaired.

Accordingly, an object of the present invention is to provide a nitride III-V which can eliminate nitrogen deficiency and efficiently grow a high quality nitride III-V compound semiconductor.
An object of the present invention is to provide a method and an apparatus for growing a group III compound semiconductor.

[0007]

Means for Solving the Problems The present inventor has made intensive studies in order to solve the above-mentioned problems of the prior art. The outline is described below.

As described above, conventionally, the growth of a GaN-based semiconductor has been performed under normal pressure or reduced pressure in the reaction tube of the MOCVD apparatus. Here, the pressure in the reaction tube is intentionally increased to 1 atm. To increase your growth. By doing so, more nitrogen source is supplied to the substrate by an amount corresponding to the increase in the pressure in the reaction tube.
Since evaporation of nitrogen from the N-based semiconductor film is also suppressed, nitrogen deficiency in the obtained GaN-based semiconductor film is eliminated, and a high-quality GaN-based semiconductor film is obtained.

In this case, it is appropriate to set the pressure in the reaction tube to 1.1 atm or more in order to obtain the effect of increasing the pressure in the reaction tube. This is for the following reasons. That is, in a normal atmospheric pressure MOCVD apparatus,
Although the exhaust side of the reaction tube is opened to the atmosphere, pressure in the reaction tube is generally several tens Torr higher than the atmospheric pressure because pressure loss occurs in the exhaust piping and the abatement apparatus. In view of this, it is appropriate to set the pressure in the reaction tube to 1.1 atm or more, with some allowance.

On the other hand, the pressure in the reaction tube naturally has an upper limit determined by the strength of the reaction tube used.
The degree of freedom in selecting the pressure is large within the range of 1 atm or more. The pressure in the reaction tube is, in principle, about 9 which is the vapor pressure of ammonia used as a nitrogen source at room temperature.
It is possible to increase the pressure up to the atmospheric pressure. However, when the pressure exceeds 2 atm, the effect of increasing the pressure tends to be saturated, and a realistic and safe pressure when using a quartz reaction tube is 2 pressure. The pressure is preferably set to 2 atm or less, for example, because the atmospheric pressure is considered to be the upper limit.

The present invention has been devised based on the above study by the present inventors.

That is, in order to achieve the above object, a first invention of the present invention is to provide a nitride III-V compound semiconductor in which a nitride III-V compound semiconductor is grown by metal organic chemical vapor deposition. The method of growing a group V compound semiconductor is characterized in that the pressure in the reaction tube is set to 1.1 atm or higher to grow a nitride III-V compound semiconductor.

A second aspect of the present invention is a reaction apparatus for growing a nitride III-V compound semiconductor, wherein the nitride III-V compound semiconductor is grown by metal organic chemical vapor deposition. The nitride-based III-V compound semiconductor is grown by setting the pressure in the tube to 1.1 atm or more.

In the present invention, typically, the growth is performed by setting the pressure in the reaction tube to 1.1 to 2 atm. Further, in order to sufficiently obtain the effect of increasing the pressure in the reaction tube and to sufficiently enhance the safety during growth, the pressure in the reaction tube is preferably set to 1.2 atm or higher.
The growth is performed at 8 atm or less, more preferably at least 1.4 atm and at most 1.8 atm, even more preferably at least 1.6 atm and at most 1.8 atm.

In the present invention, the surface of a substrate on which a nitride III-V compound semiconductor is grown may be basically upward (including obliquely upward) or downward (including obliquely downward). When the growth is performed downward, an ascending current due to thermal convection is generated in the reaction tube in a direction toward the substrate surface, so that the source gas is efficiently supplied to the vicinity of the substrate surface, and the advantage that the growth rate is increased is obtained. Can be.

In the present invention, the nitride III-V compound semiconductor contains at least one group III element selected from the group consisting of Ga, Al, In and B and at least N, and optionally further contains As. Or a group V element containing P. Specific examples of the nitride III-V compound semiconductor include GaN, AlN, and In.
N, AlGaN, GaInN, AlGaInN and the like.

In the present invention constructed as described above, the pressure in the reaction tube is set to 1.1 atm or more to grow the nitride-based III-V compound semiconductor. As compared with the case where the inside of the reaction tube is grown under normal pressure or reduced pressure, a larger amount of nitrogen material is supplied onto the substrate by the increased pressure inside the reaction tube, and the growing nitride III-V Since evaporation of nitrogen from the group III compound semiconductor film is also suppressed, nitrogen deficiency in the obtained nitride III-V compound semiconductor film is eliminated.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding portions are denoted by the same reference numerals.

First, GaN according to one embodiment of the present invention
An MOCVD apparatus used for growing a system semiconductor will be described. 1 to 6 show examples of a MOCVD apparatus.

In the MOCVD apparatus shown in FIG. 1, the reaction tube 1 is made of a material which has sufficient strength and is thermally stable, such as quartz glass. The wall of the reaction tube 1 is formed sufficiently thick so as to withstand the external pressure, that is, the pressure difference from the atmospheric pressure even when the internal pressure of the reaction tube 1 becomes 2 atm. A susceptor 2 made of, for example, graphite is provided inside a reaction tube 1, and a substrate 3 for growing is placed on the susceptor 2. An RF coil 4 is provided outside the reaction tube 1 so as to surround the reaction tube 1, and the susceptor 2 is heated by the induction heating by the RF coil 4, thereby heating the substrate 3. Has become.

A gas inlet 1a is provided at one end of the reaction tube 1, and a gas exhaust 1b is provided at the other end.
Then, the raw material gas and the carrier gas are supplied into the reaction tube 1 from the gas introduction unit 1a, and the gas in the reaction tube 1 is exhausted from the gas exhaust unit 1b and sent to the abatement apparatus (not shown). ing. A pressure adjusting component 5 is provided in the middle of the gas inlet 1a, and a pressure adjusting component 6 is provided in the middle of the gas outlet 1b.

The pressure adjusting component 5 is a component for maintaining the pressure on the downstream side at an appropriate value. Specific examples include a so-called pressure controller for controlling the pressure by a combination of a regulator, a valve and a pressure sensor. Examples include a mass flow controller, a needle valve, and a piezo valve that can indirectly control the pressure by controlling the gas flow rate. The pressure adjusting component 6 controls the cross-sectional area of the region through which the gas passes to control the difficulty of the gas flow, so that the pressure on the upstream side is kept high and the pressure of the substrate 3 on the susceptor 2 is increased. This is for stabilizing the pressure in the vicinity, and specific examples include a needle valve, a butterfly valve, a piezo valve, a thermal valve, and a solenoid valve. Using these pressure adjusting parts 5 and 6,
The inside of the reaction tube 1 can be maintained at a predetermined high pressure by appropriately adjusting the flow rates of the raw material gas and the carrier gas to be supplied.

In the MOCVD apparatus shown in FIG. 2, the entirety of the reaction tube 1 in the MOCVD apparatus shown in FIG. 1 is completely surrounded by the container 7, and when viewed from the outside, the reaction tube 1 has a double structure. . The wall of the container 7 is made of a material having sufficient strength, such as quartz glass or stainless steel, so as to be able to withstand the external pressure, that is, the pressure difference from the atmospheric pressure even when the internal pressure of the container 7 becomes 2 atm. It is formed sufficiently thick by, for example, the above. The internal pressure of the container 7 can be set to an arbitrary pressure of 1.1 to 2 atm by introducing a nitrogen gas or an inert gas from the pressure adjusting gas introducing portion 7a into the container 7 to fill the inside. Pressure can be set. by this,
Even when the internal pressure of the reaction tube 1 is set to 1.1 atm or more and 2 atm or less, the internal pressure of the reaction tube 1 is adjusted to the same pressure as the internal pressure of the reaction tube 1 or a slightly lower pressure. It is possible to avoid the danger that the reaction tube 1 will be ruptured due to the relative increase, and it is possible to stably flow the source gas into the reaction tube 1. For this reason, in this case, the wall of the main body of the reaction tube 1 has the MOCV shown in FIG.
It is not necessary to be as thick as the reaction tube 1 in the D apparatus.

The pressure adjusting gas introducing portion 7a of the container 7 is provided with a pressure adjusting component 8. This pressure adjusting component 8 is for maintaining the pressure in the container 7 stably at an appropriate value. The pressure adjusting component 5 in the MOCVD apparatus shown in FIG.
The above-mentioned specific examples are used. Reference numeral 7
b indicates a gas exhaust part of the container 7. In this case, no pressure adjusting component 6 is provided in the gas exhaust portion 1b of the reaction tube 1.

In the MOCVD apparatus shown in FIG. 3, the susceptor 2 is heated by induction heating using the RF coil 4 in the MOCVD apparatus shown in FIGS. 1 and 2, whereas the susceptor 2 is heated by the heater 9. Is going. In this case, an opening 1c is provided in a portion corresponding to the susceptor 2 in the lower wall of the reaction tube 1, and the opening 1c is provided.
The high-pressure resistant flange 10 is attached so as to block the pressure. The high-pressure resistant flange 10 is made of a material having sufficient strength, for example, stainless steel, so as to withstand a pressure difference between the inside and outside of the reaction tube 1. The heater 9 is attached to the high-pressure resistant flange 10.
The heater 9 is connected to a heater power supply 11.

In the MOCVD apparatus shown in FIG. 4, the MOCV shown in FIG.
The entirety of the reaction tube 1 in the D apparatus is completely surrounded by the container 7, and when viewed from the outside, the reaction tube 1 has a double structure.

In the MOCVD apparatus shown in FIG. 5, unlike the MOCVD apparatus shown in FIG. 1, the pressure adjusting component 5 is not provided in the gas introduction part 1a. Other configurations are the same as those of the MOCVD apparatus shown in FIG.

The MOCVD apparatus shown in FIG. 6 differs from the MOCVD apparatus shown in FIG. 2 in that a pressure adjusting part 12 is provided in the gas exhaust part 7b, and the pressure adjusting part 5 is provided outside the container 7. It is provided in the middle of a part of the gas introduction part 1a. Here, the gas introducing portion 1a and the container 7 are fixed to each other via a gasket 13 such as an O-ring, and a vacuum seal is performed. In addition, the gas introduction part 1a
And the container 7 may be directly welded to each other. The pressure adjusting component 12 is the same as the specific example of the pressure adjusting component 6 in the MOCVD apparatus shown in FIG. Other configurations are the same as those of the MOCVD apparatus shown in FIG.

Next, GaN according to an embodiment of the present invention will be described.
A method for growing a system semiconductor will be described. In this method of growing a GaN-based semiconductor, the MOCV shown in FIGS.
The GaN-based semiconductor is grown using any of the D apparatuses.

That is, first, the substrate 3 to be grown is placed on the susceptor 2 and the substrate 3 is heated to the growth temperature, and then the pressure in the reaction tube 1 is set to 1.1 to 2 atm, for example, 1.
Set to 2 atm. Next, the gas introduction part 1a is set in the reaction tube 1.
Then, a necessary source gas is supplied together with a carrier gas from the above to grow a GaN-based semiconductor on the substrate 3. Here, the substrate 3
For example, a c-plane sapphire substrate or a SiC substrate is used. Examples of the source gas include trimethylgallium (TMG) as a Ga source, trimethylaluminum (TMA) as an Al source, trimethylindium (TMIn) as an In source, ammonia (NH ₃ ) as an N source, and an n-type impurity dopant. Silane (SiH ₄ ), and cyclopentadienyl magnesium (Cp ₂ Mg) as a dopant for p-type impurities. In this case, a GaN-based semiconductor not containing In (GaN)
, AlGaN, etc.) at about 1000 ° C.
The growth temperature of a GaN-based semiconductor containing In (such as GaInN) is set to 700 to 800 ° C. in order to suppress the decomposition of InN. When a c-plane sapphire substrate is used as the substrate 3, usually 5
After growing the GaN buffer layer at a temperature of about 60 ° C., the GaN-based semiconductor is grown.

FIG. 7 shows that the pressure in the reaction tube 1 is 1.
Ga grown at 2 atm and 0.33 atm
The result of measuring the fluorescence spectrum of the N film at 77K is shown.
However, the sample used for the measurement was a GaN film grown on a c-plane sapphire substrate via a GaN buffer layer. In FIG. 7, the peak indicated by A indicates a light-emitting component called band edge emission, and it is generally considered that the higher the intensity of the peak A, the better the crystallinity.
On the other hand, in FIG. 7, B is a light-emitting component called light emission from a deep level, and it is generally considered that the smaller the intensity of B, the better the crystallinity. According to FIG.
The GaN film grown at atmospheric pressure emits light at a higher band edge and emits less light from a deep level than the GaN film grown at 0.33 atm. The result of this experiment was
This shows that the crystallinity of the obtained GaN film is improved by growing GaN while setting the internal pressure to be high.

Next, a GaN film is grown on a c-plane sapphire substrate via a GaN buffer layer, and the pressure inside the reaction tube 1 is set to 1.2 atm and 0.33 atm, respectively. A sample on which the film was grown was prepared, and the AlGaN film was observed with an optical microscope. AlGa
It is known that cracks may be formed on the surface of the N film in some cases, but the appearance of the sample in which the AlGaN film was grown at 0.33 atm was shown. On the other hand, in the sample in which the AlGaN film was grown at 1.2 atm, such a crack was not observed, and the effect of growing the sample by setting the pressure in the reaction tube 1 high was exhibited.

FIG. 8 shows that the pressure in the reaction tube 1 is 1.
In grown at 2 atm and 0.33 atm
The In composition x in _x Ga _1-x N is plotted against the supply molar ratio of In / (Ga + In) in the raw material supplied into the reaction tube 1. From FIG. 8, it is found that In is more efficiently incorporated into the grown film at a lower In / (Ga + In) supply molar ratio when grown at 1.2 atm than when grown at 0.33 atm. You can see that. This is particularly important when growing an In _x Ga ₁ -xN layer used as an active layer in the manufacture of a GaN-based light emitting device. It can be said that performing is more advantageous.

FIG. 9 shows that the pressure in the reaction tube 1 is 1.
Mg grown at 2 atm and 0.33 atm
This is a result of measuring the concentration of Mg atoms in a doped GaN sample by secondary ion mass spectrometry (SIMS). However, in each sample, undoped GaN was first grown to about 1 μm on a c-plane sapphire substrate via a GaN buffer layer, and subsequently Mg-doped GaN was grown to about 1 μm. Since there is no undoped layer at a depth deeper than 1 μm from the surface, Mg should not exist originally, but it is shown that Mg is contained in the undoped layer by diffusion from the Mg-doped layer on the surface side. . However, when the growth is performed at 1.2 atm, the decrease in Mg concentration at the boundary between the Mg-doped layer and the undoped layer is steeper, and the amount of Mg contained in the undoped layer is small. On the other hand, when growing at 0.33 atm,
The change in Mg concentration at the boundary is gradual, and the amount of Mg in the undoped layer is large. This suggests that more Mg diffuses into the undoped layer during growth at 0.33 atm, whereas such diffusion is suppressed during growth at 1.2 atm. ing. Such diffusion is a phenomenon that is unlikely to occur if the crystallinity is good, and FIG. 9 shows that a high growth pressure contributes to an improvement in crystallinity. In addition, it is important to form a steeper interface by suppressing such diffusion in device fabrication, and in that sense, a higher growth pressure is advantageous.

FIG. 10 shows the density of pits that appeared on the surface of the GaN sample grown by setting the pressure in the reaction tube 1 to 1.0 atm, 1.4 atm, and 1.6 atm, respectively. (Etch pit density) is plotted against growth pressure. From FIG. 10, 1.6
The etch pit density of the GaN sample grown at atmospheric pressure is about 3.5 × 10 ⁶ cm ⁻² , and the value of the etch pit density of the GaN sample grown at 1.0 atm is about 7.2 × 10 ⁶ It turns out that it is about 1/2 of cm- ² .
The etch pit density here is closely related to the density of defects in the crystal, and it is generally considered that the lower the etch pit density, the lower the defect density, that is, the better the crystallinity. Therefore, Ga grown at 1.6 atm
The N sample has better crystallinity than the GaN sample grown at 1.0 atm, and in that sense, growing at 1.6 atm is more advantageous than growing at 1.0 atm. It can be said that

FIG. 11 shows that S was grown by setting the pressure in the reaction tube 1 to 1.0 atm and 1.4 atm, respectively.
FIG. 4 is a plot of a threshold power density of stimulated emission by photo exitation due to photoexcitation with respect to a growth pressure for an i-doped GaN sample.
Here, the threshold power density is the minimum power density of the excitation light (light power per unit area) required for stimulated emission of light from the sample. The stimulated emission experiment was performed by irradiating laser light from a nitrogen laser from above the sample in an arrangement as shown in FIG. FIG.
1, the Si-doped GaN sample grown at 1.4 atm was better than the Si-doped GaN sample grown at 1.0 atm.
It can be seen that the threshold power density is lower than that of the sample. A low threshold power density indicates that it does not contribute to light emission such as crystal defects or that there are few elements that hinder light emission, and is considered to be a sign of higher crystallinity, that is, higher crystal quality. Can be In such an experiment, the fact that the threshold power density is low means that the threshold current is expected to be lower even in a current injection type semiconductor laser. In this sense, a higher growth pressure is more desirable.

Next, GaN according to an embodiment of the present invention will be described.
An example of a method of manufacturing a GaN-based semiconductor laser using a growth method of a based semiconductor will be described. In this method of growing a GaN-based semiconductor, the MOCVD shown in FIGS.
A GaN-based semiconductor is grown using any of the devices.
Here, a c-plane sapphire substrate is used as the substrate 3 on which the growth is performed.

First, the c-plane sapphire substrate is placed on the susceptor 2 and the c-plane sapphire substrate is heated to the growth temperature, and then the pressure in the reaction tube 1 is increased to 1.1 to 2 atm, for example, 1.2 atm. Set to. Next, a necessary raw material gas is supplied into the reaction tube 1 from the gas introduction part 1a together with a carrier gas to perform growth. In this case, first, a GaN buffer layer is grown on the c-plane sapphire substrate at a low temperature of about 560 ° C., and then a GaN-based semiconductor is grown. That is, as shown in FIG. 13, the n-type GaN contact layer 33, the n-type AlGaN cladding layer 34, and the n-type GaN optical waveguide layer are formed on the GaN buffer layer 32 thus grown on the c-plane sapphire substrate 31. 35, Ga _1-x In _x
An active layer 36 having an N / Ga _1-y In _y N multiple quantum well structure;
p-type GaN optical waveguide layer 37, p-type AlGaN cladding layer 3
8 and a p-type GaN contact layer 39 are sequentially grown. Here, as the source gas, for example, TMG is used as a Ga source, TMA is used as an Al source, and TM is used as an In source.
In, N material as NH ₃ , n-type impurity dopant as SiH ₄ , p-type impurity dopant as Cp ₂ M
Use g. In this case, the GaN-based semiconductor layer containing no In, that is, the n-type GaN contact layer 33, n
-Type AlGaN cladding layer 34, n-type GaN optical waveguide layer 3
5. The growth temperature of the p-type GaN optical waveguide layer 37, the p-type AlGaN cladding layer 38, and the p-type GaN contact layer 39 is about 1000 ° C., and the GaN-based semiconductor layer containing In, that is, Ga _1-x In _x N / The growth temperature of the active layer 36 having a Ga _1-y In _y N multiple quantum well structure is set to 700 to 800 ° C. in order to suppress the decomposition of InN. Thereafter, the p-type Ga
A heat treatment for electrically activating p-type impurities doped in the N optical waveguide layer 37, the p-type AlGaN cladding layer 38, and the p-type GaN contact layer 39 is performed.

Next, after a resist pattern (not shown) having a predetermined stripe shape is formed on the p-type GaN contact layer 39, the n-type GaN contact is formed by reactive ion etching (RIE) using the resist pattern as a mask. Etch until layer 33 is reached. Next, after removing the resist pattern, the p-type GaN contact layer 3 is removed.
9, a p-side electrode 40 having a Ni / Au structure or a Ni / Pt / Au structure is formed.
An n-side electrode 41 having an Al structure is formed. Thus, the intended GaN-based semiconductor laser is manufactured.

In the MOCVD apparatus shown in FIGS. 1 to 6, the growth is performed with the surface of the substrate 3 on which the GaN-based semiconductor is grown facing upward, but the growth may be performed with the surface of the substrate 3 facing downward. By doing so, a specific effect can be obtained as described later. FIG. 14 shows an example of an MOCVD apparatus for performing growth with the surface of the substrate 3 facing downward.

As shown in FIG. 14, in this MOCVD apparatus, a high-pressure resistant flange 10 is attached to one end on the downstream side of the reaction tube 1 and is closed. A susceptor support component 14 is attached to the high-pressure resistant flange 10. This susceptor support part 1 in the reaction tube 1
A susceptor 2 is attached to one end of the susceptor 4, and a substrate 3 for growth is fixed on the lower surface of the susceptor 2 with its surface facing downward. High pressure resistant flange 1
The gas exhaust unit 1b is located at the lower part of the reaction tube 1 just before
Is provided. A pressure adjusting component 6 is provided in the middle of the gas exhaust portion 1b. Other configurations are the same as those of the MOCVD apparatus shown in FIG.

In the MOCVD apparatus shown in FIG. 14, a raw material gas and a carrier gas flow into the reaction tube 1 from the gas introduction part 1a, and are heated near the susceptor 2 to cause a reaction. The growth of the system-based semiconductor proceeds as in the case of the MOCVD apparatus shown in FIGS. 1 to 6, except that the substrate 3 is set so that its surface faces downward. It is different from the MOCVD apparatus shown in FIGS. 1 to 6 in that a raw material gas and a carrier gas are supplied to the side. In this case, an upward airflow due to thermal convection is generated in a direction toward the surface of the substrate 3, so that the source gas is efficiently supplied to the vicinity of the surface of the substrate 3.

Next, several examples of a method of fixing the substrate 3 to the lower surface of the susceptor 2 so that the surface faces downward will be described.

In the example shown in FIG. 15, the surface around the substrate 3 located on the lower surface of the susceptor 2 is supported from below by a substrate retainer 15, and the substrate retainer 15 is screwed to the susceptor 2 with a screw 16. 3 is a method of fixing to the lower surface of the susceptor 2. Here, the substrate retainer 15 may have a shape that covers the entire surface of the substrate 3, or may have a shape that presses a small part of the surface around the substrate 3 like a nail, and may have various shapes. May be.

The example shown in FIG. 16 is a method of fixing the substrate 3 to the lower surface of the susceptor 2 by pressing the surface around the substrate 3 with a spring 17 attached to the lower part of the susceptor 2.

FIG. 17 shows a cylindrical frame 18 having a diameter slightly larger than that of the substrate 3 and having a substrate support 18a.
In this method, the substrate 3 is fixed to the lower surface of the susceptor 2 by placing the substrate 3 inside the susceptor 2 and fitting the susceptor 2 inside the frame 18 from above. FIG. 18 is a perspective view showing this state.

In the example shown in FIG. 19, a small exhaust passage 19 reaching the lower surface of the susceptor 2 is provided inside the susceptor 2, and the substrate 3 is evacuated from the exhaust passage 19 by a vacuum pump. Is a method of vacuum chucking and fixing to the lower surface of the device. At this time, by appropriately selecting the degree of evacuation, the flow of the source gas and the carrier gas is prevented from being adversely affected by the evacuation.

In the MOCVD apparatus shown in FIG.
Although the surface of the substrate 3 faces directly downward, it is not necessary that the surface of the substrate 3 directly downward. As shown in FIG. 20, the normal to the surface of the substrate 3 on which the GaN-based semiconductor is grown has a downward component. That is, it may be obliquely downward.

Next, with the surface of the substrate 3 facing downward, the GaN
An example of a growth condition when growing a system semiconductor will be described. That is, TMG was used as a Ga raw material at 25 μmol / min, N
By flowing NH ₃ at a flow rate of 0.1 mol / min as a raw material, a GaN film having good crystallinity can be grown. A typical flow rate when the growth is performed using the same reaction tube 1 with the surface of the substrate 3 facing upward, when the flow rate of TMG is 25 μmol / min, the flow rate of NH ₃ is 0.2 to 0.1 / min.
3 mol, so less NH ₃
It can be said that a GaN film having good crystallinity can be efficiently grown with the supplied amount.

As described above, according to this embodiment,
Since the growth of the GaN-based semiconductor is performed by setting the pressure in the reaction tube 1 to a pressure of 1.1 to 2 atm, the growth is performed with the inside of the reaction tube at normal pressure or reduced pressure as in the related art. As compared with the case where the process is performed, a higher nitrogen pressure is supplied to the substrate by the higher pressure in the reaction tube, and the evaporation of nitrogen from the growing GaN-based semiconductor film is also suppressed. And the high-quality GaN-based semiconductor film can be grown.

In particular, by growing a GaN-based semiconductor with the surface of the substrate 3 facing downward, the following advantages can be obtained. That is, when a GaN-based semiconductor is grown by the MOCVD method, the growth temperature is high. Therefore, if the growth is performed with the surface of the substrate 3 facing upward, the rising airflow due to the thermal convection on the substrate 3 is large, and the source gas is not effective. There is a concern that it is difficult to reach directly above the substrate 3 and that N and the like may be released again from the grown crystal. As a result, it is necessary to increase the growth efficiency with respect to the supply of the source gas and to improve the crystallinity. difficult. On the other hand, when the growth is performed with the surface of the substrate 3 facing downward, an upward airflow due to thermal convection occurs in a direction toward the surface of the substrate 3. Therefore, the source gas is effectively carried to the surface of the substrate 3 by the rising airflow, and the concentration of the source gas near the surface of the substrate 3 is effectively increased, so that the growth proceeds efficiently and the nitrogen pressure is reduced. Since the desorption of N and the like can be suppressed by the larger addition, the crystallinity is also improved. In particular, under the condition that the pressure in the reaction tube 1 during the growth is higher than the normal pressure as in this embodiment, not only the crystallinity is improved by increasing the growth pressure, but also the surface of the substrate 3 is directed downward. By doing so, the effects of improving the growth efficiency and the crystallinity are also added, and a very good quality GaN-based semiconductor film can be grown.

By manufacturing a GaN-based semiconductor laser as shown in FIG. 13 using the growth method according to this embodiment, a high-performance and long-life GaN-based semiconductor laser can be realized.

As described above, one embodiment of the present invention has been specifically described. However, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. .

For example, M shown in FIGS. 1 to 6 and FIG.
The OCVD apparatus is merely an example, and the MO
A CVD device may be used. Specifically, the susceptor 2 may be heated by a lamp, an electric furnace, or the like.

[0055]

As described above, according to the present invention, the pressure in the reaction tube is set to 1.1 atm or more to grow the nitride III-V compound semiconductor. It is possible to solve the problem of insufficient nitrogen in the nitride-based III-V compound semiconductor to be grown. For example, when growing a nitride-based III-V compound semiconductor containing indium, indium is efficiently incorporated into the grown film. When impurity doping is performed, a steep impurity concentration distribution can be obtained, and good crystallinity can be obtained. Then, a high-quality nitride-based III-V compound semiconductor can be efficiently grown.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first example of a MOCVD apparatus used for growing a GaN-based semiconductor in one embodiment of the present invention.

FIG. 2 is a schematic diagram showing a second example of a MOCVD apparatus used for growing a GaN-based semiconductor in one embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a third example of a MOCVD apparatus used for growing a GaN-based semiconductor in one embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a fourth example of an MOCVD apparatus used for growing a GaN-based semiconductor in one embodiment of the present invention.

FIG. 5 is a schematic diagram illustrating a fifth example of an MOCVD apparatus used for growing a GaN-based semiconductor in one embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a sixth example of an MOCVD apparatus used for growing a GaN-based semiconductor in one embodiment of the present invention.

FIG. 7 is a schematic diagram showing a measurement result of a fluorescence spectrum at 77 K of a GaN film grown by setting the pressure in a reaction tube of an MOCVD apparatus to 1.2 atm and 0.33 atm, respectively.

FIG. 8 shows In / (Ga +) of In composition x in In _x Ga _1-x N grown by setting the pressure in the reaction tube of the MOCVD apparatus to 1.2 atm and 0.33 atm, respectively.
(In) A schematic diagram showing the dependence on the supply molar ratio.

FIG. 9 shows the results of measuring the concentration of Mg atoms in Mg-doped GaN grown by setting the pressure in the reaction tube of the MOCVD apparatus to 1.2 atm and 0.33 atm by secondary ion mass spectrometry. FIG.

FIG. 10 shows the results of measuring the growth pressure dependence of the etch pit density in GaN grown by setting the pressure in the reaction tube of the MOCVD apparatus to 1.0 atm, 1.4 atm, and 1.6 atm, respectively. FIG.

FIG. 11 shows S grown by setting the pressure in the reaction tube of the MOCVD apparatus to 1.0 atm and 1.4 atm, respectively.
FIG. 9 is a schematic diagram illustrating a result of measuring a growth pressure dependency of a threshold power density of i-doped GaN.

FIG. 12 is a schematic diagram for explaining a method of measuring a threshold power density shown in FIG. 11;

FIG. 13 is a cross-sectional view for explaining an example in which the method of growing a GaN-based semiconductor according to one embodiment of the present invention is applied to the manufacture of a GaN-based semiconductor laser.

FIG. 14 is a schematic diagram showing an example of an MOCVD apparatus used for growing a GaN-based semiconductor with the substrate surface facing down in one embodiment of the present invention.

FIG. 15 is a cross-sectional view showing a first example of a method of fixing a substrate to a lower surface of a susceptor so that the surface faces downward.

FIG. 16 is a cross-sectional view showing a second example of a method of fixing a substrate to the lower surface of a susceptor so that the surface faces downward.

FIG. 17 is a cross-sectional view showing a third example of a method of fixing a substrate to a lower surface of a susceptor so that the surface faces downward.

FIG. 18 is a perspective view for explaining a third example of a method of fixing a substrate to the lower surface of a susceptor so that the surface faces downward.

FIG. 19 is a cross-sectional view showing a fourth example of a method of fixing a substrate to the lower surface of a susceptor so that the surface faces downward.

FIG. 20 is a cross-sectional view for explaining an example in which growth is performed with the surface of the substrate facing obliquely downward.

[Explanation of symbols]

1 ... reaction tube, 1a, 7a ... gas introduction part, 1b,
7b: gas exhaust unit, 2: susceptor, 3: substrate, 4: RF coil, 5, 6, 8, 12: pressure adjusting component, 7: container, 8 ... ·heater

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsunori Yanashima 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Masao Ikeda 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo No. Sony Corporation

Claims (8)

[Claims] 1. A method for growing a nitride-based III-V compound semiconductor by growing a nitride-based III-V compound semiconductor by metalorganic chemical vapor deposition, comprising: A method for growing a nitride-based III-V compound semiconductor, wherein the growth is performed at a pressure equal to or higher than the atmospheric pressure. 2. The pressure in the reaction tube is 1.1 atm or more.
2. The method according to claim 1, wherein said nitride-based III-V compound semiconductor is grown at a pressure lower than the atmospheric pressure.
The method for growing a nitride-based III-V compound semiconductor according to the above. 3. The nitride-based III-V compound semiconductor is grown by setting the pressure in the reaction tube to 1.2 atm or more and 1.8 atm or less. The method for growing a nitride-based III-V compound semiconductor according to (1). 4. The method according to claim 1, wherein the pressure in the reaction tube is set to 1.4 atm or more and 1.8 atm or less to grow the nitride III-V compound semiconductor. The method for growing a nitride-based III-V compound semiconductor according to (1). 5. The method according to claim 1, wherein the pressure in the reaction tube is set to 1.6 atm or more and 1.8 atm or less to grow the nitride III-V compound semiconductor. The method for growing a nitride-based III-V compound semiconductor according to (1). 6. The method for growing a nitride III-V compound semiconductor according to claim 1, wherein the surface of said substrate on which said nitride III-V compound semiconductor is grown faces downward. . 7. A nitride III-V compound semiconductor growth apparatus in which a nitride III-V compound semiconductor is grown by a metal organic chemical vapor deposition method. An apparatus for growing a nitride-based III-V compound semiconductor, wherein the nitride-based III-V compound semiconductor is grown at an atmospheric pressure or higher. 8. The nitride III according to claim 7, wherein the substrate is held such that the normal to the surface of the substrate on which the nitride III-V compound semiconductor is grown has a downward component. -An apparatus for growing a group V compound semiconductor.