CN1037283C - Apparatus and method for preparing nitride single crystal film by gas phase epitaxy of metal organic compound - Google Patents

Abstract

The present invention provides a device and a method for growing GaN and a monocrystal film of associated compounds of GaN. A coaxial double-tube flow divider respectively transports NH3 gas and an organic source in a III group, and can conveniently adjust a mixing point of the NH3 gas and the organic source in a III group so as to rapidly mix the two kinds of gas and expand the gas in a laminar flow mode. The present invention can furthest reduce gas-phase side reaction. A gas-flow compression type MOVPE reaction system can obtain even GaN with high quality and monocrystal films of associated compounds of GaN. The present invention can improve a use factor of materials by 6 to 7 times. The present invention can be used for the production and the research of a GaN-based blue LED or an LD, and can also be used for the application research of GaN electronic devices with high temperature and high power, etc.

Description

Method and device for preparing nitride single crystal film by metal organic matter vapor phase epitaxy

The invention provides a method and a device for preparing a nitride single crystal film by metal organic matter vapor phase epitaxy, which relates to the preparation of a III-V group nitride semiconductor single crystal film and is directly related to the preparation technology of a blue Light Emitting Diode (LED) based on gallium nitride (GaN).

The nitride semiconductor materials of III-V group include gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN) and its multi-component alloy system, such as indium gallium nitride (InGaN), aluminum gallium nitride (AlGaN) etc. these nitrides are all direct band gap semiconductor materials in α phase, the forbidden band widths of InN, GaN, AlN are 1.9eV, 3.39eV, 6.2eV respectively, the forbidden band widths of InGaN and AlGaN are varied with the composition, the luminescence wavelength which can be nearly linearly varied from 1.9eV to 3.39eV and from 3.39eV to 6.2 eV. covers the whole visible light to ultraviolet band, especially the application of blue light to ultraviolet band photoelectric devices, which arouses extensive attention and research.

In the production of nitride semiconductor materials, Vapor Phase Epitaxy (VPE) has been the main method in the early days, and Metal Organic Vapor Phase Epitaxy (MOVPE) and Molecular Beam Epitaxy (MBE) have been the main techniques in recent years. The most advanced and effective is the MOVPE technique, in which ammonia NH is usually used₃As a source of N, high purity hydrogen H₂As a carrier gas. Trimethyl gallium (TMGa), trimethyl aluminum (TMAl) and trimethyl indium (TMIn) are used as Ga, Al and In sources. Using c-plane alumina Al₂O₃(0001) The single crystal wafer is used as a substrate due to nitride and Al₂O₃Large lattice mismatch and thermal stress mismatch exist between substrates, and a two-step growth method is often adopted for epitaxial growth. See documents H.Amano, N.Sawaki, and Y.Toyoda, appl.phys.Lett.48(5), 353(1986) and Shuji Nakamumra, Jpn.J.appl, phys.30(10A), L1708 (1991). Namely, growing an AlN or GaN layer as a transition layer at low temperature, and then growing an epitaxial layer at high temperature. However, due to NH₃Has stronger gas phase side reaction with a III group organic source, and seriously influences the crystal quality and the utilization efficiency of source materials. By NH₃With TMAl for example, the major gas phase side reactions are:

thereby resulting in (-NH)₃Al-NH-)_nAnd (4) forming a complex. This complex is not involved in the AlN-producing reaction. And therefore must be suppressed. But during the epitaxial growth, NH is required₃And mixed homogeneously with a group III organic source to obtain a homogeneous epitaxial growth. Therefore, such side reactions are technically only minimized,but not completely eliminated. Another problem is due to NH₃A particular in fluid dynamics. For MOVPE of other III-V compounds, the primary transport gas is H₂The reactant gas flow rates are all very small. Fluid characteristics substantially consisting of H₂Is determined. In the process of nitride MOVPE, NH₃The flow rate of gas is very large, sometimes approaching or exceeding H₂The flow rate of gas. The gas flow properties are therefore influenced by NH₃The effect of (c) is not negligible. And H₂Compared withNH₃The higher the Plantt number Pr ═ uC/k ═ v/α of gas, this means NH₃Ratio of kinematic viscosity to temperature coefficient of thermal conductivity, or NH₃The ratio of the diffusivity of motion (or velocity) to the diffusivity of heat (or temperature) is large. Large temperature gradients tend to develop over the substrate for locally heated MOVPE systems, resulting in considerable thermal buoyancy that prevents the reactant gases from contacting the substrate surface. Therefore, the existence of gas phase side reaction and thermal buoyancy not only seriously affects the quality of nitride crystal, but also greatly reduces the utilization rate of materials. The very low growth rate of nitrides has been a major problem in practical applications.

To solve these problems, many methods have been tried, such as using hydrazine, phenylhydrazine, tert-butylamine, etc. as N source instead of NH₃Or using some organic compounds containing N-R (R can be Ga, Al and In) bonds to grow related compounds such as GaN and the like; and with NH₃Or N₂In order to lower the growth temperature of gallium nitride (GaN). However, none of these methods has been significantly improved. The best results are currently obtained with the bis proposed by Nakamura et al, Japan Riyama chemical industries, IncFlow MOVPE, see Shuji Nakamura Yasuhiro Harada, and Maayuki Seno, applied phys. Lett.58, 2021(1991), involves the addition of an auxiliary gas flow in a horizontal chamber in addition to the reactant gas input in the horizontal direction, in a direction perpendicular to the substrate surface, to increase the contact of the reactant with the substrate surface. However, this would certainly destroy the laminar flow characteristics of the gas. Therefore, to address the uniformity of the epitaxial layers, they use a method of rotating the substrate, adding complexity to the apparatus and operation. FUJITSU LIMITED, applied to European patentoffice No. 0505249A1 on 3/16.92, discloses a method and Apparatus for preparing semiconductor material of ternary compound of II-VI group and above, which uses baffle plates to separate and transport reactant gas, and the purpose of separating the former gas flow into an upper gas flow region and a lower gas flow region, so that the reactant which is generated with large capacity is mixed and preheated to enhance the reaction, thereby achieving the purpose of uniform components. However, the baffle plate can only divide the gas into an upper structure and a lower structure, and reactant gases are difficult to be uniformly mixed before reaction. And the method and apparatus cannot solve the problem of thermal buoyancy generated at an extremely high growth temperature in the preparation of nitride semiconductor materials.

The invention aims to solve the problems of gas phase side reaction and thermal buoyancy in the preparation of nitride semiconductor materials, improve the utilization rate of the materials and the crystal quality of an epitaxial layer and enhance the uniformity of epitaxial growth.

Contents and technical scheme of the invention

The method adopts Metal Organic Vapor Phase Epitaxy (MOVPE) technology, NH₃As a source of N, high purity H₂As carrier gas, TMGa, TMAl as Ga, Al, In source, c-face alumina Al₂O₃(0001) Using the single chip as a substrate, and forming a H film on the substrate₂+ TMR and NH₃The reactant gases are respectively transported by coaxial inner and outer pipelines, and the gas outlet point of the inner pipeline is a gas mixtureThe gas is mixed in front of the reaction chamber and then enters the reaction chamber for laminar flow expansion, a reaction tube with an inclined angle α on the upper wall and an inclined angle theta of a graphite heater on the lower wall are adopted in the reaction chamber,and (3) compressing airflow above the substrate, and growing a transition layer at a low temperature and then growing an epitaxial layer at a high temperature by adopting a two-step growth method.

The diameter of the inner pipe is 3mm, the diameter of the outer pipe is 3.5mm, the air flow range of the inner pipe and the outer pipe is 1-4Slm (standard liter per minute), the pressure of the reaction chamber is 40-100 torr, the distance between the mixing point and the front end of the air flow expansion zone is 1-2 cm, the inclination angle α of the mixing point can be adjusted to be 3-6 degrees through the length of the inner pipe, and the inclination angle theta is 7-10 degrees.

Apparatus for use in the above method comprising: the gas transport system comprises a coaxial double-pipe flow divider consisting of a coaxial inner pipe and a coaxial outer pipe, and NH is introduced into the gas transport system₃Gas and H₂The + TMR gas is respectively introduced into the inner tube and the outer tube and is led to an air inlet tube of a reaction system, the reaction system adopts a compression type MOVPE reaction tube and comprises the air inlet tube, an air flow expansion area, a rectangular area, an air flow compression area and a rear exhaust area, an inclined angle of the upper tube wall of the reaction tube is α, an inclined angle of a graphite heater on the lower tube wall of the reaction tube is theta, air flow compression above the surface of a substrate is formed, the position of an air outlet point of the inner tube of the coaxial double-tube flow divider is a mixing point of the gas, and the position of the mixing point can be adjusted by adjusting the length of the.

The outer pipe of the coaxial double-pipe shunt adopts a 3.5mm stainless steel pipe, the inner wall of the outer pipe is processed by electrochemical polishing, the inner pipe is a stainless steel pipe with the diameter of 3mm, the inner pipe and the outer pipe of the inner pipe are processed by electrochemical polishing, and the inner pipe and the outer pipe are connected by a reducer union sealed by polytetrafluoroethylene. The position of the mixing point is 1-2 cm at the front end of the airflow expansion area.

The width-height ratio of the rectangular area of the compression type MOVPE reaction tube is 4-9, the angle of the airflow expansion area is 6-30 degrees, the inclination angle of the upper wall of the quartz reaction tube is 3-6 degrees, and the inclination angle of the graphite heater on the lower tube wall is 7-10 degrees. The positions of the top wall inclined to the top points of the inclination angles of the graphite heaters are vertically symmetrical.

The invention has the advantages and positive effects that:

the quality inspection results of the grown sample through a Scanning Electron Microscope (SEM), reflection high-energy electron diffraction (RHEED), x-ray diffraction (XRD), light fluorescence (PL) spectrum, Auger electron spectrum and Hall measurement show the advantages and positive effects of the invention.

1. Coaxial double-barrelled shunt:

under the above experimental conditions, provided NH is present₃The distance between the air inner pipe and the front end of the airflow expansion area is about 1cm, so that NH can be generated₃And H₂The gas borne group III organic source achieves thorough mixing as shown in fig. 2 (a). When the NH3 tube extends into the expansion region of the flow in the reaction chamber, it is not easy to achieve sufficient mixing, as shown in FIG. 2 (b). This is due to the outer tube gas flow and the inner tube gas flow expanding outwards at the same time, and the NH₃The air flow is relatively large, so that H containing TMR₂Difficulty in gas flow to NH₃The airflow zone expands. Their mixing is mainly achieved by means of gas phase diffusion processes. In the case of fig. 2(a), the two gases meet in a small area and thus are easily mixed with each other. Then enters an airflow expansion area, and laminar flow expansion is conveyed to the surface of the substrate. Under our experimental conditions, the gas flow rate was approximately 2-4 m/S. The time required from the gas flow mixing point to the substrate surface is approximately 0.25-0.5S. So in such a short time, twoThe gas flow is well mixed and transported to the substrate surface, which is very advantageous for suppressing gas phase side reactions.

2. Compression type MOVPE reaction chamber

A number of experimental results show that under the above experimental conditions, the optimum α angle is 3 ° -6 °, the optimum θ angle is 7 ° -10 °, when the θ angle is greater than 15 °, strong vortex recirculation is induced in front of the graphite heater, when the α angle is greater than 7 °, laminar flow characteristics are destroyed, resulting in uneven growth, and when α ° is 0 ° and θ<5 °, island-like growth, slow growth rate and poor crystal quality are often caused.

In a generally horizontal rectangular MOVPE reaction chamber (i.e., α ═ 0 °, θ<5 °), only the graphite heater is locally heated in the reaction chamber due to rf heatingThe mixed flow determined by the convection is shown in fig. 3 (a). While free convection away from the substrate surface is NH due to the high growth temperature of GaN₃Large flow rate, and NH₃The Prandtl number and the Grashof number of (g) are both large and the variation is particularly significant, resulting in a large reactant concentration gradient over the substrate, making the reactant concentration of GaN at the substrate surface rare. In addition, GaN has high decomposition pressure (N) at 1030 DEG C₂Equilibrium partial pressure of about 0.8atm), and thus GaN is grown in N₂Under partial pressure. This results in the formation of a large number of N vacancies in the GaN film, which have negative donor levels, and thus GaN films often have a high N-type background concentration.

In addition, according to the theory of continuous medium fluid dynamics, the relative velocity change and the relative sectional area change of the compressible fluid are that the fluid velocity is increased when the fluid sectional area is reduced.

3. The method of the invention can rapidly grow high-quality single crystal film

Under the conditions of example 1, the growth rate of GaN was 3.5 μm/hr at a TMGa flow rate of 11.9 μmole/min, which is equivalent to 7 times the growth rate we had in the conventional MOVPE reaction chamber under the same experimental conditions. The growth rate per unit TMGa flow is increased by a factor of 3.6 compared to the dual flow MOVPE system of Nakamura et al.

By adopting the method, the obtained high-quality GaN growth surface is bright like a mirror surface, has no growth defect characteristics, and is colorless and transparent under the optimized experimental conditions. The SEM photograph is shown in FIG. 4 (a). Although the GaN surface grown under the optimized conditions of the conventional MOVPE reaction chamber is macroscopically bright, the growth can still be seen under a high power SEMLong defect features, as shown in the SEM image of fig. 4 (b). This improvement in surface morphology is a result of the co-action of a compression type MOVPE reaction chamber with a coaxial double tube shunt with appropriate growth conditions. FIG. 5 is c-plane Al₂O₃Growth on a substrateRHEED graph of GaN film. Wherein (a) is in<2110>Diffraction of electrons in the directions (b) are<0110>Directional electron diffraction. FIG. 6(a) shows c-plane Al₂O₃X-ray double-crystal diffraction pattern of gallium nitride (GaN) film grown on substrate, wherein 2 theta angle is from 10 deg. to 80 deg., and only GaN (0002) and (0004) and Al₂O₃(0006) The diffraction peak of (1). These results indicate that the (0001) GaN single crystal thin film is grown on (0001) Al₂O₃On a substrate of (1). Figure 7 is a slow-scan XRD at 2 theta from 32 deg. to 43 deg.. The diffraction peak at 34.6 ° was measured accurately as the diffraction of (0002) plane of GaN having lattice constant a of 3.189A and c of 5.185A, c/a of 1.6259, which is very close to the theoretical value of 1.633, and the bimorph pendulum curve of x-ray diffraction, which is an important parameter for characterizing crystal quality, is shown in fig. 8. The full width at half maximum (FWHM) was 6 minutes. FIG. 9 is the PL spectrum at 15k with N as excitation source of λ 337.1nm₂A molecular laser. At a wave number of 28260cm^-1(wavelength. lambda. ═ 353.857nm) at the main peak, the band edge emission peak, and the wave number 17857cm^-1The broad weak peak at (560 nm) is the emission band associated with impurity emission. Is generally considered to be related to the impurity C.

Fig. 10 is a depth profile of auger electron spectra of InGaN samples grown in example 2. It can be seen from the figure that the In composition is uniformly distributed In the longitudinal direction. FIG. 11 is PL spectrum of InGaN sample at room temperature, with a lasing source of He-Cd laser, lasing wavelength of 325.0nm and PL peak position of 394.7nm, corresponding to In_xGa_1-xThe value of x for N is 0.11.

FIG. 12 shows Al on the r-plane in example 3₂O₃XRD pattern of gallium nitride (GaN) single crystalthin film grown on substrate. The very strong diffraction peak at 57.7 ° for 2 θ is the GaN (1120) diffraction. I.e. (0112) Al₂O₃The growth surface of the substrate (GaN) is the (1120) plane. FIG. 13 is the PL spectrum of this sample at 11K, the diffraction source is a He-Cd laser with a wavelength of 325.0nm, the peak at 359.0nm is the band edge emission peak of GaN at 11KNo emission peaks related to impurities were present.

The above samples had better thickness uniformity than. + -. 2% over a diameter of 30 mm. Hall measures the background carrier concentration of undoped GaN, with the best results being 4.9X 10¹⁶cm^-3Room temperature Hall mobility of 303.1cm²/V.S。

These results are sufficient to show that high quality GaN and InGaN single crystal thin films have been obtained using the present invention.

In summary, the present invention provides for the first time a novel method for growth of GaN and related compounds by compressive MOVPE with coaxial dual tube shunt. With this system, high quality GaN and InGaN single crystal thin films were grown at pressures of 40-70 Torr. This system can also be used to grow other III-V nitride semiconductor single crystal thin films such as AlGaN, AlN, and InN, as well as multilayer heterostructures. The growth rate was increased 7-fold over the conventional MOVPE system and 3.6-fold over the Nakamura et al dual stream MOVPE system. Can be used for preparing GaN-based blue LED and other nitride devices. Is beneficial to reducing the cost in application and improving the utilization efficiency of materials and the crystal quality. Therefore, the method has wide application value and economic benefit.

Description of the drawings:

FIG. 1 is a schematic diagram of acoaxial dual tube shunt and compression type MOVPE reaction system

1-coaxial double-tube shunt outer tube and connection part of outer tube and MOVPE gas transportation system

2-inner tube 3-polytetrafluoro A reducer union

4-quartz reaction tube and stainless steel system B reducer union

5-A reducer union position 6-inner tube air outlet position namely air flow mixing point

7-quartz reaction chamber inlet pipe 8-airflow expansion area

9-rectangular zone 10-gas stream compression zone

11-rear exhaust area 12-graphite heater

13-thermocouple tube 14-substrate slice

FIG. 2 is a mixed flow diagram of gas flow for a coaxial dual tube splitter delivery system

(a) The mixing point of the air flow is selected to be suitable

(b) Conditions of improper selection of mixing point for air streams

FIG. 3 gas flow lines and velocity components at growth temperature in a compression type MOVPE reaction chamber

(a) Case of conventional MOVPE reaction chamber

(b) Case of compression type MOVPE reaction chamber

FIG. 4 Al₂O₃SEM photograph of GaN surface grown on substrate

(a) Samples grown in coaxial double tube splitter compression-type reaction chambers

(b) Samples grown in conventional reaction chambers

FIG. 5 RHEED plot of growth samples from a coaxial dual tube splitter compression-type reaction chamber

(a) -2110>direction electron diffraction

(b) -direction<0110>

FIG. 6X-ray diffraction, 2 θ Angle 10 ° to 80 ° fast Scan, of example 1 GaN grown sample

FIG. 7X-ray diffraction, Slow-Scan at 2 θ of 32 to 43 ° for GaN sample grown in example 1

FIG. 8 x-ray diffraction twin crystal rocking curve of GaN sample grown in example 1

FIG. 9 PL spectra of GaN samples grown in example 1, temperature was 15K, and lasing light source was N₂Molecular laser

FIG. 10 longitudinal depth distribution of Auger electron spectra of InGaN samples grown in example 2

FIG. 11 PL spectra of InGaN grown in example 2, temperature 300K, lasing source He-Cd laser

FIG. 12X-ray diffraction Pattern of GaN grown in example 3

FIG. 13 PL spectra of GaN samples grown in example 3, at a temperature of 11K, with a lasing light source of a He-Cd laser

Example (b):

a schematic diagram of a coaxial dual tube shunt and compression type MOVPE reaction chamber is shown in figure 1. The coaxial double-tube shunt comprises an outer tube 1, an inner tube 2, a reducing joint A3 and a reducing joint B4. The compression type MOVPE reaction chamber can be divided into an inlet pipe 7, a gas flow expansion zone 8, a rectangular zone 9, a gas flow compression zone 10 and a rear exhaust zone 11.

Can react NH with₃The outer tubes of the MOVPE gas delivery system (not shown) and the coaxial double-tube shunt for respectively delivering the group III organic source are respectively made of phi₁3.5mm stainless steel tube. And are joined as shown at 1 in figure 1. NH (NH)₃Gas enters the phi through the A reducer union 3₂An inner tube 2 of stainless steel electrochemically polished 3mm inner and outer tube walls was kept separate from the TMR source. A reducer union and (H)₂The connection of the + TMR) tubes is to be taken care of keeping smooth, as shown at 5 in fig. 1, ensuring that there is no dead space for the gas flow. The stainless steel pipe is connected with the quartz reaction pipe through the B reducing joint 4. The reducing joint B is connected with the stainless steel pipe by adopting a sealing joint and is connected with the quartz pipe by adopting a high-temperature sealing ring. NH (NH)₃Gas flow with (H)₂The + TMR) gas flows meet at the inner tube gas outlet point 6, which is the mixing point of the gases. The position of the mixing point 6 can be adjusted by adjusting the length of the inner tube. The rate of thorough mixing of the two gases and the diameter phi of the inlet tube 7 of the quartz reaction tube₃(8-12mm), the angle of the reaction tube extension, and the experimental conditions. The gas flow rate can be adjusted by changing the pressure in the reaction chamber and the gas flow rate. Thereby determining the time at which the mixed gas reaches the surface of the substrate. The principle of the above adjustment is as follows: when the gas reaches the surface of the substrate under the condition of meeting the epitaxial growth, the gas can be fully mixed in the shortest time and spread in a laminar flow manner. Thus, the gas phase side reaction can be minimized, and the uniform growth of the whole substrate surface can be ensured.

The angle of the gas flow expansion area of the gas flow compression type MOVPE reaction chamber can be selected from 6-30 degrees, the width-to-height ratio of the rectangular area is 4-9, the gas flow compression area is formed by the inclination angle α of the upper wall of the reaction tube and the inclination angle thetaof the graphite heater on the lower tube wall, as shown in 10 in figure 1, just above the substrate, the optimal α angle and the optimal theta angle can be adjusted according to specific experimental conditions in a matching way, and the optimal gas flow compression effect is obtained on the premise of ensuring laminar flow.

In specific implementations, the common experimental conditions are: in all experiments, TMGa, TMAl, TMIn and NH were used₃As a source of Ga, Al, In and N. High purity H₂As a carrier gas. Double-side polished Al₂O₃As a substrate. The heating mode is radio frequency heating. The temperature is monitored by thermocouple 13 inserted into the graphite heater at 12 in fig. 1 and controlled by a temperature controller. The substrate is placed in position in the graphite heater 14.

In addition, Al should be dealt with in the specific operation₂O₃The substrate is first ultrasonically cleaned with carbon tetrachloride, acetone and ethanol and 1HPO₃∶3H₂SO₄The mixed solution is corroded for 10 minutes at 160 ℃. After rinsing with deionized water, vacuum dewatering, in N₂Loading into reaction chamber under gas protection, and before epitaxial growth, adding Al₂O₃Substrate at H₂The treatment was carried out under an atmosphere at 1150 ℃ for 10 minutes.

Example 1.

c-plane Al₂O₃(0001) Growing gallium nitride (GaN) on a substrate

This example was conducted in a reaction chamber at α ° 3 ° and θ 10 °, the pressure in the chamber was 70 torr, and after the above common experimental procedure was completed, the substrate temperature was lowered to 550 ℃, a gallium nitride (GaN) transition layer, H, was grown₂The gas flow rate is 1Slm, NH₃The flowrate was 4Slm, the TMGa flow rate was 7.1. mu. mole/min, and the thickness of the gallium nitride (GaN) transition layer was about 25 nm. The substrate temperature was then raised to 1030 ℃ and the TMGa flux was changed to 11.9 μmole/min, with the remaining conditions unchanged, and the growth time was 1 hour, with a gallium nitride (GaN) layer thickness of about 3.5 μm.

Example 2.

c-plane Al₂O₃(0001) Growth of InGaN on a substrate

After completion of example 1, the substrate temperature was lowered to 900 deg.C, the TMIn flow rate was 18.8. mu. mole/min, the TMGa flow rate was 4.8. mu. mole/min, the rest of the conditions were unchanged, and the growth time was 30 minutes. The thickness of InGaN is about 0.5 μm.

Example 3.

r-plane Al₂O₃(0112) Growing gallium nitride (GaN) on a substrate

This example was conducted in a reaction chamber at α ° 5 ° θ 5 °, the pressure in the chamber was 40 torr, and after the above common experimental procedure, the substrate temperature was lowered to 600 ℃ to grow an AlN transition layer, H₂Gas flow rate and NH₃The flow rates are all 2Slm, the TMAl flow rate is 2.6 mu mole/min, and the AlN transition layer thickness is 50 nm. The substrate temperature was then raised to 1030 ℃ to grow gallium nitride (GaN). The TMGa flow rate was 9.5. mu. mole/minute, the growth time was 1 hour, and the thickness was about 2.0. mu.m.

Claims (11)

1. A method for preparing nitride single crystal film by metal organic gas phase epitaxy (MOVPE) technique and NH₃As N source, high purity H₂As carrier gas, TMGa, TMAl and TMIn are used asGa, Al and In source, c-face Al₂O₃(0001) The single crystal wafer is used as a substrate, the heating is performed by radio frequency, the temperature is monitored by a thermocouple (13) inserted into a graphite heater and controlled by a temperature controller, the substrate is placed at a position above the graphite heater, and NH is introduced into the substrate₃Gas and H₂Transporting the + TMR reactant gas to an MOVPE reaction chamber, adopting a two-step growth method, firstly growing a transition layer at a low temperature (400-650 ℃), and then growing an epitaxial layer at a high temperature (more than 1000 ℃), wherein the method is characterized in that NH is added into the reaction chamber₃Gas and H₂The + TMR reactant gas is respectively transported by an inner pipeline and an outer pipeline before entering the MOVPE reaction chamber, the gas outlet point of the inner pipeline is a gas mixing point, the gas is mixed before the reaction chamber, the upper wall of the reaction tube of the reaction chamber is provided with an inclination angle α, the inclination angle theta of a lower wall graphite heater is 3-6 degrees, the angle theta is 7-10 degrees, and gas flow compression is carried out above the substrate.

2. A metal alloy as claimed in claim 1A process for preparing the monocrystal nitride film by vapor-phase epitaxy of organic substance features that NH is respectively introduced to internal and external tubes₃And H₂+ TMR (R is Ga, Al, In or compound thereof) reactant gas, the diameter of the inner tube is 3mm, the diameter of the outer tube is 3.5mm, the gas flow range of the inner tube and the outer tube is 1-4Slm, the pressure of the reaction chamber is 40-100 Torr, the position of the mixing point can be adjusted by the length of the inner tube, and the distance between the mixing point and the front end of the gas flow expansion zone is 1-2 cm.

3. A method for preparing a nitride single crystal thin film by metal organic vapor phase epitaxy as defined in claim 1, wherein the pressure in the reaction chamber is 40 to 70 Torr, the gas flow ranges from 1 to 4Slm for the inner and outer tubes, and the angles of α and θ are adjustable.

4. A method for producing a nitride single-crystal thin film by metalorganic vapor phase epitaxy as defined in claim 1, 2 or 3, wherein the conditions for growing the epitaxial layer of gallium nitride (GaN) and the related III-V nitride semiconductor single-crystal thin film are:

the mixing point is 1cm away from the front end of the airflow expanding area, α is equal to 3 degrees, theta is equal to 10 degrees, and the pressure of the reaction chamber is 40-70 torr;

the growth temperature of the GaN transition layer is 500-600 ℃, the growth temperature of the AlN transition layer is 600-650 DEG C

The growth temperature of the GaN epitaxial layer is 900-1030 DEG C

The growth temperature of the InGaN epitaxial layer is 800-900 DEG C

H₂The gas flow is 1-2SlmNH₃The air flow is 1-4Slm

The TMGa flow is 5-7 mu mole/min when growing the transition layer, and is 7-20 mu mole/min when growing the epitaxial layer;

TMAl flow rate is 2-4 mu mole/min when growing the transition layer;

the TMIn flow rate is 5-20. mu. mole/min when InGaN is grown, and the TMGa flow rate is 4-5. mu. mole/min at this time.

5. The method for producing a nitride single crystal filmby metallorganic vapor phase epitaxy according to claim 4, wherein Al is used as the Al component₂O₃The substrate is first ultrasonically cleaned with carbon tetrachloride, acetone and ethanol and 1HPO₃∶3H₂SO₄Corroding the mixed solution at 160 ℃ for 10 minutes; after rinsing with deionized water, vacuum dewatering, in N₂Loading into reaction chamber under gas protection, and before epitaxial growth, adding Al₂O₃Substrate at H₂The treatment was carried out under an atmosphere at 1150 ℃ for 10 minutes.

6. An apparatus for use in the method of claim 1, comprising: gas transport system, reaction system and pressure and temperature control system, characterized by:

1) the gas transportation system comprises a coaxial double-pipe flow divider, which consists of a coaxial inner pipe and a coaxial outer pipe, and NH is introduced into the gas transportation system₃Gas and H₂The + TMR gas is respectively introduced into the inner pipe and the outer pipe and is communicated with an air inlet pipe of the reaction system;

2) the reaction system adopts a compression type MOVPE reaction tube, which comprises an air inlet tube, an airflow expansion area, a rectangular area, an airflow compression area and a rear exhaust area, wherein the upper tube wall of the reaction tube is provided with an inclination angle of α, the inclination angle of a graphite heater on the lower tube wall is theta, α is 3-6 degrees, and theta is 7-10 degrees;

3) the position (6) of the outlet point of the inner pipe (2) of the coaxial double-pipe flow divider is the mixing point of the gas, and the mixing point is positioned before the gas flow expansion zone.

7. Theapparatus according to claim 6, wherein the outer tube of the coaxial double tube shunt is made of a stainless steel tube having a diameter of 3.5mm and the inner wall of the outer tube is treated by electrochemical polishing, the inner tube of the shunt is made of a stainless steel tube having a diameter of 3mm and the inner and outer tube walls of the inner tube are treated by electrochemical polishing, and the inner and outer tubes are connected by a teflon-sealed reducer union (3).

8. The device according to claim 6, wherein the position of the air outlet point of the inner tube of the coaxial double-tube splitter can be adjusted by the length of the inner tube, and is 1-2 cm in front of the air flow expansion area.

9. Push buttonThe apparatus for vapor-phase epitaxy of metal-organic compounds for producing nitride single-crystal films as claimed in claim 6, wherein the reaction system is a compression type MOVPE reaction tube having a rectangular area with an aspect ratio of 4 to 9, a flow spreading area angle of 6 to 30 °, an upper wall inclination α of the quartz reaction tube of 3 to 6 °, a graphite heater on a lower tube wall with an inclination angle θ of 7 to 10 °, and a diameter Φ of an inlet tube (7) of the reaction tube₃Is 8-12 mm.

10. The apparatus of claim 6 wherein the upper tube wall inclination angle α in the compression MOVPE reaction tube and the graphite heater inclination angle θ on the lower tube wall are adjustable and the apex of the two angles α and θ start at positions that are symmetrical up and down.

11. The apparatus according to claim 6, characterized in that at the inlet end of the coaxial double tube splitter, a reducer union (3) is used to connect the inner tube and the outer tube coaxially, a reducer union (4) is used at the other end of the splitter and the connection with the stainless steel tube is realized by a sealing joint and the connection with the reaction tube is realized by a high temperature sealing ring.

Images