JPH10242053A - Gallium nitride semiconductor device and method of manufacturing gallium nitride semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an amorphous state buffer layer free from surface uneven ness, by forming a GaN single crystal buffer layer whose film thickness is specified, on the surface of a substrate. SOLUTION: Since a natural oxide film sticks on a substrate, the film is eliminated by increasing the substrate temperature. After the substrate temperature is set at, e.g. 700 deg.C and then stabilized, irradiation with Ga and dimethyl hydrazine is started. When the surface is observed by using a high speed electron beam diffraction equipment (RHEED), spots of GaN are appearing between spot rows showing a sapphire substrate. The growth of GaN is stopped when the RHEED spots do not vanish, e.g. after 5 minutes. The RHEED pattern shows that the GaN surface is flat in the atomic order and GaN is composed of single crystal. By Auger measurement and a transmission electron microscope, it can be confirmed that the film thickness of GaN is at most 3nm, e.g. equivalent to 2nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high quality Ga
The present invention relates to a GaN-based semiconductor device having an N-based semiconductor layer and a method of manufacturing the same, and more particularly, to a structure of a buffer layer capable of improving the quality of a GaN-based semiconductor layer and a method of manufacturing the same.

[0002]

2. Description of the Related Art Various types of semiconductor devices such as transistors and optical elements are manufactured by laminating one or more semiconductor layers on a substrate serving as a base, and subjecting them to desired patterning by etching or doping techniques. It is produced by performing or additionally forming necessary electrodes.

[0003] GaN-based semiconductors are expected to be used as optical element materials in the visible to ultraviolet region or as electronic materials that can be used in high-temperature regions, and the development of high-quality GaN-based semiconductor devices has been desired. Since GaN has a melting point exceeding 2000 ° C. and a high vapor pressure at the melting point, it is difficult to manufacture a GaN single crystal substrate to be a base.

For this reason, a GaN-based semiconductor device must be manufactured by growing a GaN-based semiconductor layer on a heterogeneous substrate such as sapphire. However, since the lattice constants of sapphire and the GaN-based semiconductor differ by more than 20%, It is difficult to epitaxially grow a GaN-based semiconductor layer directly on a sapphire substrate.

Therefore, conventionally, amorphous AlN or amorphous GaN is formed on a sapphire substrate.
There has been used a method of forming a buffer layer made of GaN, and forming a GaN-based semiconductor layer in which a single layer or a plurality of layers of GaN, AlGaN, InGaN or the like are stacked on the buffer layer.

In order to form an amorphous buffer layer, the growth temperature may be lower than normal epitaxial crystal growth conditions. For example, an amorphous GaN buffer layer may be formed at a temperature of about 500 to 600.degree. Growth by vapor phase epitaxy (MOCVD) or 5
It can be formed by growing at about 00 to 550 ° C. by gas source molecular beam epitaxy (GSMBE).

[0007]

According to the above-mentioned method, it is possible to grow a GaN-based semiconductor layer using a heterogeneous substrate such as sapphire or the like so as to obtain a temporary LED light emission, but the quality is still insufficient. Not higher quality Ga
It has been desired to realize a GaN-based semiconductor device having an N-based semiconductor layer.

Further, the conventional method has a problem that it is not easy to control the surface state of the amorphous buffer layer. That is, under the above-described conditions for forming the amorphous buffer layer, the growth starts in an island shape, so that the buffer layer thickness must be equal to or more than a certain value in order to enhance the surface smoothness. As the thickness increases, the crystalline state changes from an amorphous state to a polycrystalline state, and the surface becomes rough. However, since the surface state cannot be observed during film formation by RHEED or the like due to the amorphous state, it has been difficult to obtain an amorphous buffer layer having no irregularities on the surface.

[0009]

SUMMARY OF THE INVENTION The present invention has solved the above-mentioned problem, and has a GaN film having a thickness of 3 nm or less on a substrate surface.
A GaN-based semiconductor device having a single crystal buffer layer, comprising: growing a GaN single crystal buffer layer on a substrate surface;
A method of manufacturing a GaN-based semiconductor device, comprising growing a base-based semiconductor layer, irradiating a substrate surface with 1 to 2 monolayers of Ga, growing a GaN single-crystal buffer layer, and further forming the GaN single-crystal buffer layer. A method for manufacturing a GaN-based semiconductor device, comprising growing a GaN-based semiconductor layer on a buffer layer, wherein the GaN single-crystal buffer layer is grown after a GaAs substrate or a GaP substrate is heat-treated under arsenic pressure or phosphorous pressure. And growing a GaN-based semiconductor layer on the GaN single-crystal buffer layer.
This is a method for manufacturing an aN-based semiconductor device.

According to the present invention, an ultra-thin (3 nm or less) buffer layer made of GaN single crystal is formed on a substrate surface, and the crystal quality of a GaN-based semiconductor film formed thereon is extremely good. It was completed by finding the target.

The present invention can be applied not only to a sapphire substrate but also to a Si substrate, a GaAs substrate, and a GaP substrate. In any case, a GaN-based semiconductor layer having a very high-quality GaN-based semiconductor layer is used. A semiconductor device can be obtained.

In the present invention, a GaN single crystal is a crystal state in which the crystal directions are aligned to such an extent that a streak-like diffraction pattern can be obtained by RHEED (for example, a specular state of a GaN crystal formed under the condition of an acceleration voltage of 25 KeV). (A crystal state in which the intensity of the beam spot is at least 5 times the intensity of the specular beam spot of the substrate crystal), and includes a state in which the crystals are formed into domains when the crystal directions are aligned. .

In the present invention, the buffer layer made of GaN single crystal preferably has a thickness of 3 nm or less. The reason is that it is difficult to grow a GaN single crystal of 3 nm or more, which may cause defects or the like.

In order to form a buffer layer made of GaN single crystal on the substrate surface, metal organic chemical vapor deposition (MOC)
In the case of using the VD method, a growth temperature of 800 to 900 ° C. (substrate surface temperature during growth) is preferable, and in the case of using the molecular beam epitaxial growth method (MBE method), 650 to 75.
A growth temperature of 0 ° C. is preferred. In this case, the nitrogen raw materials include dimethylhydrazine, ethylazide (C2H5N3), nitrogen that has been turned into plasma, and high decomposition efficiency.
The use of radicalized nitrogen or cracked ammonia is preferable because the growth time can be shortened, and in particular, the use of dimethylhydrazine or ethylazide improves the properties of the GaN single crystal buffer layer and forms the GaN single crystal buffer layer on the GaN single crystal buffer layer. The crystallinity of the GaN-based semiconductor layer can be made extremely high.

The surface of the substrate is irradiated with one or two monolayers of gallium to bring the surface of the substrate into a Ga-rich state, and then the growth of the GaN single crystal buffer layer is started. Can be effectively prevented, and the GaN single crystal can be easily formed on the entire surface of the substrate.

When a GaAs substrate or a GaP substrate is used, the surface of the substrate can be made Ga-rich by heat treatment under arsenic pressure or phosphorous pressure. In this state, the GaN single crystal buffer layer is grown. Similarly, the quality of the GaN single crystal buffer layer can be improved.

According to the present invention, high-quality G which has never existed before
A GaN-based semiconductor device having an aN-based semiconductor layer can be obtained. Furthermore, the surface condition of the buffer layer was changed to RHE
Since the film can be formed while observing with the ED, the reproducibility of the quality of the buffer layer can be enhanced, and the variation in the characteristics of the GaN-based semiconductor layer formed on the buffer layer can be reduced. Having.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a description will be given of a semiconductor growth apparatus used for carrying out an embodiment of the present invention.

As shown in FIG. 1, the apparatus is an ultrahigh vacuum apparatus having an introduction chamber (load lock chamber), a preparation chamber, and a growth chamber. The device configuration will be described. The introduction chamber is provided with a turbo molecular pump (displacement: 500 l / sec) combined with a rotary pump so that vacuum can be evacuated from atmospheric pressure to an ultra-high vacuum of 10 ⁻¹⁰ Torr, and between the turbo molecular pump and the vacuum chamber. A gate valve is installed so that the pump can be disconnected at any time. Furthermore, an ion pump (displacement 50
0 l / sec). A gate valve is provided between the ion pump and the introduction chamber for the same reason as described above. At the center of this vacuum chamber, a rotatable substrate holder is installed so that the substrate can be transferred to another vacuum chamber, and the substrate once installed in this holder is transferred from the introduction chamber to the preparation room and further to the growth chamber. A transfer rod for transport is installed such that the central axis of the transfer rod coincides with the substrate holder. In these three chambers, the preparation chamber and the load lock chamber are connected by a gate valve, and the preparation chamber and the growth chamber are connected by a gate valve. Further, all of these vacuum chambers are provided with viewing windows so that the delivery of the substrate can always be observed.

In the preparation room, a substrate holder capable of heating the substrate is provided at the center thereof. Vacuum evacuation was performed using an ion pump (displacement volume 500 l / sec) at 1 × 10
High vacuum evacuation up to ^-11 Torr is possible.
Before the substrate introduced in the preparation chamber is put into the growth chamber, the substrate is once heated in this chamber at a relatively low temperature (at a temperature of 200 to 500 ° C. depending on the type of the substrate) for the purpose of removing moisture and the like.

The growth chamber contains organic materials necessary for growth,
A quadrupole mass spectrometer (QMS) for analyzing a metal raw material, a substrate heater reaction gas, and a high-speed electron beam diffractometer (RHEED) for in-situ observation of the growth state are provided.

First, nozzles such as dimethylhydrazine (DMHy, (CH3) 2NNH2) as a source gas of nitrogen and ammonia gas are provided. Dimethylhydrazine is filled in a 50cc cylinder, and it is precisely controlled to a desired flow rate using a Granbell Phillips variable leak valve that can be ultra-precisely controlled through a 1/4 inch stainless steel pipe from the cylinder. It can be introduced. Ammonia gas is 1
The gas is filled in a 0 liter cylinder, passed through a stainless steel pipe of 1/4 inch size, precisely controlled through a mass flow controller through a mass flow controller, and can be introduced into the growth chamber similarly to the above-mentioned gas.

Knudsen cells of metal gallium (Ga), aluminum (Al), and indium (In), which are Group III raw materials used for crystal growth, are provided in the growth chamber. Further, Knudsen cells (K cells) each having a one-stage heater structure for magnesium (Mg) for doping and silicon (Si) are similarly installed.

To briefly explain the structure of the cell, a crucible having a capacity of 100 cc made of high-purity PBN is installed in the center of the cell, and the raw material is charged therein. A heater made of tantalum is wound around the outside of the crucible so as to cover the entire outer periphery of the crucible, and a heat shielding plate is wound around the outside of the heater to prevent heat from being released.

By precisely controlling the temperature of this heater using a temperature controller, the temperature of the raw material is precisely controlled, the vapor pressure of the raw material is precisely controlled, and the flux required for the growth is precisely controlled. Adjust to. The above-mentioned K cell can be opened and closed instantly by an automatic shutter opening / closing mechanism which can be controlled by a computer, and can instantaneously switch between introducing or shutting off the raw material to the substrate surface, thereby obtaining a steep growth interface.

At the center of the growth chamber, a manipulator having a substrate heating mechanism is provided. This manipulator can be finely adjusted independently in the X-axis, Y-axis, and Z-axis, and further has a rotating mechanism. The substrate can be set on a holder having a heating mechanism of the manipulator. As the substrate heating heater, a heater having a diameter of 3 inches is used. The temperature control of this substrate heater and all the above-mentioned cells uses FICS11 of a precision controller made by Eurotherm, and the power supply of these cells and the substrate heater uses a stabilized DC power supply to minimize power supply fluctuation. Used. These power supply and temperature controller are connected to a computer and perform precise temperature control by computer control. The temperature fluctuation of the growing cell is kept within 0.5 ° C.

A QMS is provided so that a reaction gas or a product gas used for the growth can be analyzed, so that gas analysis can be performed before, during, or after the growth. Further RH
The state of the growing crystal surface can be observed in real time by EED. A flux gauge for sequentially measuring the flux of the raw material is provided.

(Example 1) Ga using a sapphire substrate
An N-based semiconductor device was manufactured. The sapphire substrate is first wet etched. The sapphire substrate is organically cleaned using an ultrasonic cleaner, etched with heated hot phosphoric acid, cleaned with ultrapure water, and placed in a load lock chamber shown in FIG. After the load lock chamber is sufficiently evacuated to 5 × 10 ⁻⁸ Torr using a turbo pump or an ion pump, the gate valve between the preparation chamber and the load lock chamber is opened, and the load lock chamber is prepared from the load lock chamber using a transfer rod. Transfer the substrate to the chamber. After the vacuum chamber has reached 1 × 10 ⁻⁹ Torr after being placed in the preparation room, the substrate heater is heated to 500 ° C. and held for 15 minutes to remove moisture on the substrate surface. After cooling to 200 ° C. or lower, the substrate is transferred from the preparation room to the growth room.

During the series of operations, in the growth chamber, the temperature of each K cell was increased to adjust the flux of the raw material and the flow rates of dimethylhydrazine and ammonia gas so that they could be started at any time, and the shutter was closed. Keep it in a state. First, when the temperature of the K cell is a Ga cell, the heater is set to 900 ° C. and the Ga flux is adjusted so that the vacuum degree of the flux gauge becomes 6.0 × 10 ⁻⁷ Torr. At this time, the temperature fluctuation of the cell heater is ±
The temperature is controlled to be within 0.2 ° C. That is, the fluctuation of the flux is suppressed to 1% or less. In the case of Al, the heater temperature is set to 1000 ° C. and the flux is adjusted so as to be 3.0 × 10 ⁻⁷ Torr by the vacuum degree of the flux gauge. Similarly, the fluctuation of the flux is suppressed to 1% or less. In the case of In, the cell temperature is set to 750 ° C., and the flux is 3.0 × 10 ⁻⁷ Torr at the vacuum degree of the flux gauge.
Adjust to r. Similarly, the temperature of the Si cell for the dopant is adjusted to 1280 ° C. so that the flux has a flux gauge vacuum of 5.0 × 10 ⁻⁹ Torr. For Mg, the cell temperature was set to 220 ° C., and the flux was 5.0 × 10 ⁻⁹ at a vacuum degree of a flux gauge.
Adjust to Torr. In each cell, the fluctuation of the flux is suppressed to 1% or less. Close the shutter so that you can start anytime after adjustment.

In the case of dimethylhydrazine, a variable leak valve that can be precisely adjusted is used, and its flux is 4.0 × 10 −5 Torr at a vacuum of a flux gauge.
Adjust so that The fluctuation of the flux is suppressed to 1% or less. Only the main valve is closed so that it can be started at any time after adjustment.

In the case of ammonia, the flow rate of the gas is adjusted to 4 sccm using a mass flow controller, and the degree of vacuum of the flux gauge is 6.0 × 10 ⁻⁶ Torr.
Adjust to r. In each cell, the fluctuation of the flux is suppressed to 1% or less. Close the shutter so that you can start anytime after adjustment.

A series of adjustment operations are performed while the substrate is being heated and cooled in the preparation room. After the above operation is completed, the substrate is transferred from the preparation room to the growth room. After being transported to the growth chamber,
After the degree of vacuum in the growth chamber reaches 1 × 10 ⁻⁹ Torr, Ga
Enter the growth process for N-related materials. After attaching the substrate to the substrate heating holder of the manipulator, the substrate is rotated at a rotation speed of 10 to 20 rpm until the growth is completed.

As shown in FIG. 2A, a natural oxide film is adhered to the substrate, and is removed by raising the temperature of the substrate (FIG. 2B).

Next, a GaN single crystal buffer layer is grown. When the substrate temperature is stabilized at 700 ° C., irradiation of Ga and dimethylhydrazine is started.
At this time, the Ga flux was 6.0 × 10 ⁻⁷ Torr, and the irradiation amount of dimethylhydrazine was 4 × 10 ⁻⁵ Torr.
And

Observation by RHEED shows that GaN
Spots begin to appear between the rows of spots indicating the sapphire substrate. Where the specular spot indicating the sapphire substrate does not completely disappear, that is, the RHE of the underlying substrate
The GaN growth is stopped where the ED spot does not disappear (FIG. 2 (c)). The time required during this time was 5 minutes. At this time, the RHEED pattern indicating GaN becomes a streak-like spot, indicating that it is a single crystal, and the specular spot on the sapphire substrate remains without disappearing. This RHEED pattern indicates that the surface of GaN is flat in atomic order and that GaN is a single crystal.

At this time, it was confirmed by Auger measurement and transmission electron microscope that the film thickness of GaN was equivalent to 2 nm. When the growth is completed with the GaN RHEED pattern, the GaN film thickness becomes 2 nm with good reproducibility,
In-situ observation by ED was very effective for film thickness control and crystal evaluation.

Next, a GaN-based semiconductor layer is grown. Here, the nitrogen source is changed from dimethylhydrazine to ammonia. The reason for this is that when GaN is grown thick with dimethylhydrazine, a large amount of carbon is mixed into the crystal, making it difficult to obtain a high-purity crystal, and using ammonia to obtain a high-purity crystal.

First, the shutters of Ga and dimethylhydrazine are closed immediately after the end of nitriding. Thereafter, when the substrate temperature is raised to reach 850 ° C., ammonia is irradiated.

After irradiating the surface of the GaN single crystal buffer layer with ammonia, the temperature of the substrate is brought to within 0.1 ° C., and then a Ga shutter is opened to open a predetermined flux of Ga (6.0 × 10 ⁻⁷ Torr). ). The time required from the irradiation of ammonia to the irradiation of Ga is about 5 minutes. This starts the growth of GaN. Temperature fluctuation during growth is suppressed within 0.1 ° C. at a set temperature, and flux fluctuation is suppressed to 1% or less. As the growth progresses, the surface temperature of the grown crystal surface shifts (the temperature shifts toward higher temperatures for non-doped and n-type impurity doping, and to lower temperatures for p-type impurity doping). Uses a color thermometer from the viewing window,
While monitoring the temperature with the naked eye every 5 minutes, the set temperature is changed so as to correct the changed temperature so that the surface temperature is always kept constant. The growing RHEED pattern is Ga
It shows a streak-like pattern of N, which means that GaN is a single crystal and the surface is very smooth. Thus, growth was performed for 2 hours (FIG. 2D). After growth, the film thickness was measured to be 500 nm.
Met. When the crystal surface after growth was observed using a Nomarski microscope or the like, it was confirmed that no surface defects were observed and the surface had a mirror surface.

Further, a sample was prepared in which the thickness of the GaN single crystal buffer layer was changed, and the GaN
The crystal state of the semiconductor layer was evaluated. That is, a growth time of 1, on a sapphire substrate treated under the same conditions as described above,
A GaN single-crystal buffer layer was formed under the same conditions as described above except for 3, 7, 9, and 11 minutes, and the film thickness was measured by Auger measurement.
1.2, 2.8, 3.5, and 4.5 nm.

Next, for each of these samples, G
When a 500-nm GaN-based semiconductor film was grown on the aN single-crystal buffer layer, the RHEED pattern during the growth of the GaN-based semiconductor layer was G
It shows a streak-like pattern of aN, and it was confirmed that the GaN-based semiconductor layer was a single crystal and the surface was very smooth. When the crystal surface after growth was observed using a Nomarski microscope or the like, it was confirmed that no surface defects were observed and the surface had a mirror surface. Meanwhile, growth time 7,
Many surface defects and surface roughness were observed for the samples at 9 and 11 minutes. From the above results, it was found that a thin and flat GaN single crystal buffer layer having an atomic order of 3 nm or less before growing a GaN thick film is effective for growing a high-quality GaN thick film.

Furthermore, a high-quality GaN-based semiconductor film could be similarly obtained by doping Mg or Si under the above-mentioned flux conditions in growing a GaN thick film. or,
After growing an ultra-thin (3 nm or less) GaN single-crystal buffer layer and a GaN-based semiconductor film, In, Ga, and ammonia are simultaneously irradiated under the above flux conditions to grow InGaN thickly, or when Al, Ga, and ammonia are grown. Even when AlGaN was grown thick by simultaneous irradiation under the above flux conditions, the finally obtained crystal surface showed a mirror surface, and it was confirmed that the obtained crystal was a high quality epitaxial film.

(Example 2) After irradiating the substrate surface with 1-2 monolayers of Ga in advance and growing a GaN single crystal buffer layer under the same conditions as in Example 1,
An N-based semiconductor device was manufactured. That is, after processing the sapphire substrate under the same conditions as in Example 1, the temperature of the sapphire substrate was set to 700 ° C., and the Ga flux was 6.
After irradiating 0 × 10 ⁻⁷ Torr of Ga for 10 seconds, a GaN single crystal buffer layer (with a growth time of 5 minutes) and a GaN-based semiconductor layer were grown under the same conditions as in Example 1.

The RHEED pattern showing GaN of the sample manufactured in this embodiment is more streak (linear) in the RHEED pattern showing GaN, and it is confirmed that the flatness of the surface is further improved. Was.

(Embodiment 3) Next, it will be shown that an ultra-thin GaN single crystal buffer layer is effective for improving the quality of a GaN-based semiconductor layer even when a Si substrate is used. First, Si (11
1) After performing the organic cleaning of the substrate for 15 minutes, the substrate is immersed in hydrofluoric acid for 5 minutes, taken out of the hydrofluoric acid, immediately put into a load lock chamber, and starts evacuation. After the load lock chamber is sufficiently evacuated to 5 × 10 ⁻⁸ Torr using a turbo pump or an ion pump as described above, the gate valve between the preparation chamber and the load lock chamber is opened, and the load is loaded using the transfer rod. The substrate is transferred from the lock chamber to the preparation chamber. After the vacuum chamber reached 1 × 10 ⁻⁹ Torr after the wafer was placed in the preparation room, the substrate heater was turned on for 5 hours.
Heat to 00 ° C. and hold for 15 minutes to remove moisture and the like on the substrate surface. After cooling to 200 ° C. or lower, the substrate is transferred from the preparation room to the growth room.

During the above series of operations, in the growth chamber, the temperature of each K cell is increased as described above to adjust the flux of the raw material and the flow rates of dimethylhydrazine and ammonia gas so that they can be started at any time. Keep the shutter closed.

After the above operation is completed, the substrate is transferred from the preparation room to the growth room. After being transported to the growth chamber, the degree of vacuum in the growth chamber reaches 1 × 10 ⁻⁹ Torr, and then the process of growing a GaN-related material is started. First, the temperature of the substrate is started. As shown in FIG. 2B, the natural oxide film on the substrate surface is removed. Thereafter, when the substrate temperature was lowered to 700 ° C. and the temperature was stabilized, the Ga cell shutter was opened and Ga was removed.
G of flux with a flux of 6.0 × 10 ⁻⁷ Torr
a, and after 10 seconds, irradiate with dimethylhydrazine. When observed by RHEED, a spot of GaN starts appearing after 1 minute. Where the specular spot indicating the Si (111) substrate does not completely disappear, that is, the RHE of the base
Stop the growth of GaN where the ED spot does not disappear. The time required during this time is 4-5 minutes. At this time, the RHEED pattern indicating GaN becomes a streak-like spot, indicating that it is a single crystal, and the specular spot on the sapphire substrate remains without disappearing. This R
The HEED pattern indicates that the surface of GaN is flat on the atomic order and that GaN is a single crystal.

At this time, it has been confirmed that the thickness of GaN is equivalent to 2 nm by Auger measurement or the like. The above GaN
When growth is completed with RHEED pattern of G
The aN film thickness became 2 nm, and in-situ observation by RHEED was very effective for film thickness control and crystal evaluation.

Further, when GaN was grown to a thickness of 500 nm on the buffer layer under the same conditions as in Example 1, the surface after the growth became a mirror surface as in the case of the sapphire substrate. Further, even if Mg or Si is doped under the above-mentioned flux conditions in the growth of a GaN thick film, similarly high quality Ga
An N-based semiconductor layer was obtained. After growing the GaN single crystal buffer layer and the GaN-based semiconductor layer, the In,
When Ga and ammonia are simultaneously irradiated under the above flux conditions to grow InGaN thickly, or when Al, Ga,
Simultaneously irradiating ammonia under the above flux conditions
Even when GaN is grown thick, the crystal surface finally obtained shows a mirror surface, confirming that it is a high quality epitaxial film. At this time, the thicknesses of InGaN and AlGaN were 500 nm.

Therefore, it was shown that the ultra-thin GaN single crystal buffer layer was also effective for growing a GaN-based semiconductor film on a Si substrate.

(Embodiment 4) When a GaAs or GaP substrate is used, these crystals have a structure in which only Ga is arranged on the uppermost surface in terms of structure. That is, when heated in an ultra-high vacuum, the uppermost surface of the crystal can be a Ga plane. Therefore, in this case, the substrate surface can be made to be in a Ga-rich state without irradiating Ga before producing the GaN single crystal buffer layer. For example, when a GaAs or GaP substrate is heated in an ultra-high vacuum while irradiating arsenic pressure or phosphorous pressure, and the substrate temperature is set to 600 to 580 ° C., its surface is observed as a streak (1 × 1) Ga-rich surface by RHEED. Becomes A gallium plane that is flat on the order of atoms can be formed.

In the case of GaAs, the natural oxide film is removed at a substrate temperature of 620 ° C. and under an arsenic pressure (1.5 × 10 ⁻⁶ Torr). At this time, since the surface after removing the oxide film is rough, the substrate temperature is lowered to 580 ° C.
× 10 ⁻⁷ Torr) and arsenic (1.5 × 10 ⁻⁶ Torr)
A GaAs epitaxial film that is flat in the atomic order is formed at about 500.degree. Next, the irradiation of gallium was stopped and the substrate temperature was raised to 610 ° C.
When the As surface is observed with RHEED, a streak (1 ×
1) It becomes a Ga-rich surface.

When the surface is irradiated with dimethylhydrazine set to the above-mentioned flux for 15 minutes to stop the supply of arsenic, a GaN single crystal buffer layer having the same quality as that of the second and third embodiments can be obtained.

In the case of GaP, a flat GaN single crystal buffer layer can be formed in the atomic order by the same method as in the case of GaAs. In the case of GaP, the native oxide film is removed at 650 ° C. under a phosphorous pressure (1.5 × 10 ⁻⁶ Torr).
At this time, since the surface after removing the oxide film is rough, the substrate temperature is lowered to 600 ° C., and the metal gallium (1.5 × 1
While simultaneously irradiating with 0 ^-7 Torr and phosphorous (1.5 × 10 ^-6 Torr), a flat epitaxial layer of GaP on the order of atoms is formed at about 500 °. Next, when the gallium irradiation is stopped and the substrate temperature is raised to 620 ° C., the GaP surface becomes a streak (1 × 1) Ga-rich surface when observed by RHEED.

When the surface is irradiated with dimethylhydrazine set to the above-mentioned flux for 15 minutes to stop the supply of arsenic, a GaN single crystal buffer layer having the same quality as that of the second and third embodiments can be obtained.

In the above embodiments, the case where dimethylhydrazine is used as the nitrogen source used for growing the GaN single crystal buffer layer has been described. However, other than the above, ethylazide having high decomposition efficiency, nitrogen that has been turned into plasma, nitrogen that has been radicalized, It is also possible to use cracked ammonia.

[0057]

According to the present invention, a high-quality GaN film for producing optical and electronic devices can be formed. In particular, a blue light emitting device and an electronic device which can operate at high temperature and high withstand voltage can be manufactured. It has tremendous industrial benefits in the fields of industry, satellite communications and the munitions industry.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a semiconductor growth apparatus used in an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a process according to an embodiment of the present invention.

Claims (4)

[Claims] 1. A GaN-based semiconductor device comprising a GaN single crystal buffer layer having a thickness of 3 nm or less on a substrate surface. 2. A method of manufacturing a GaN-based semiconductor device, comprising: growing a GaN single-crystal buffer layer having a thickness of 3 nm or less on a substrate surface, and then growing a GaN-based semiconductor layer on the GaN single-crystal buffer layer. Method. 3. The method of manufacturing a GaN-based semiconductor device according to claim 2, wherein a GaN single crystal buffer layer is grown after irradiating the substrate surface with one to two monolayers of Ga. 4. The GaN single crystal buffer layer is grown after a GaAs substrate or a GaP substrate is heat-treated under arsenic pressure or phosphorous pressure.
A method for manufacturing an N-based semiconductor device.