CN102820211A - Non-polar A-plane GaN film preparation method - Google Patents

Abstract

The invention provides a non-polar A-plane GaN film preparation method including: growing a non-polar A-plane InGaN flexible layer on a substrate; growing a non-polar A-plane GaN buffer layer on the non-polar A-plane InGaN flexible layer; annealing the non-polar A-plane InGaN flexible layer and the non-polar A-plane GaN buffer layer to form a self-assembly laterally epitaxial template; and growing a non-polar A-plane GaN film on the self-assembly laterally epitaxial template. By the aid of the self-assembly nanoscale laterally epitaxial template, film quality can be improved, and non-polar GaN films high in crystalline quality are obtained.

Description

Method for preparing non-polar A-plane GaN thin film

technical field

The invention relates to the technical field of semiconductor thin film preparation, in particular to a method for preparing nonpolar GaN thin film.

Background technique

In the past few decades, GaN and related alloy semiconductor materials such as InGaN and AlGaN have achieved great success. This has also promoted the rapid development of light-emitting diodes (LEDs), laser diodes (LDs) and high electron mobility transistors (HEMTs) in the semiconductor field.

Although remarkable achievements have been made in the field of GaN semiconductor materials, in the hexagonal nitride materials grown on the traditional C-plane, the spontaneous polarization and piezoelectric polarization existing along the C-direction cause a strong built-in electric field inside the material. Seriously hinder the further improvement of the performance of related devices. In order to reduce the influence of the polarization electric field on the luminous efficiency of quantum wells, the growth of non-polar A-plane GaN has become the focus of research. The sapphire substrate meets the requirements of mass industrialization due to its price advantage. Therefore, the use of R-plane sapphire substrates to grow non-polar A-plane GaN thin films has also received more and more attention.

However, due to the large lattice mismatch and thermal mismatch between nonpolar A-plane GaN and R-plane sapphire substrates, high-density stacks often exist in A-plane GaN films grown on R-plane sapphire substrates. Stacking faults and dislocations, the material quality is poor, and many current methods for improving C-plane GaN defects are not ideal when applied to non-polar A-plane GaN films.

Contents of the invention

(1) Technical problems to be solved

In order to solve one or more of the above problems, the present invention provides a method for preparing a non-polar GaN film, so as to improve the crystal quality of the non-polar GaN film.

(2) Technical solution

According to one aspect of the present invention, a method for preparing a non-polar A-plane GaN thin film is provided. The method includes: growing a non-polar A-plane InGaN flexible layer on a substrate; growing a non-polar A-plane GaN buffer layer on the non-polar A-plane InGaN flexible layer; annealing the A-plane GaN buffer layer to form a self-assembled lateral epitaxial template; and growing a non-polar A-plane GaN thin film on the self-assembled lateral epitaxial template.

(3) Beneficial effects

It can be seen from the above technical scheme that the method for preparing non-polar GaN thin film of the present invention has the following beneficial effects:

(1) Previous studies have shown that it is difficult to obtain high-quality epitaxial films by two-step epitaxial growth of non-polar GaN films directly on the R-face sapphire, but the use of the self-assembled nanoscale lateral epitaxial template of the present invention can improve film quality and obtain films with Non-polar GaN films with higher crystal quality;

(2) Compared with MBE growth technology, MOCVD material growth technology has been widely used in industrial production due to its relatively low cost and simple operation. The method of the present invention has a high growth rate, reaching 1 μm/hr, At the same time, the growth quality is better.

Description of drawings

FIG. 1 is a flow chart of preparing a non-polar A-plane GaN thin film according to an embodiment of the present invention;

2 is a schematic diagram of temperature changes in the process of preparing a non-polar A-plane GaN thin film according to an embodiment of the present invention;

3 is a schematic cross-sectional structure diagram of a non-polar A-plane GaN thin film prepared according to an embodiment of the present invention;

Fig. 4 is the SEM image of the non-polar A-face GaN film prepared by the conventional two-step method (A) and the method (B) shown in Fig. 1;

FIG. 5 is a graph showing the variation of the rocking half-width with the azimuth angle of the non-polar A-plane GaN film prepared by the conventional two-step method and the method shown in FIG. 1 .

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

In an exemplary embodiment of the present invention, a method for preparing a non-polar GaN thin film is provided. As shown in Figure 1, the method includes the following steps:

Step A: taking a substrate, and performing high-temperature nitriding treatment on the substrate in a reaction chamber of a metal-organic chemical vapor deposition (MOCVD) device;

Place the R-side sapphire substrate in the metal-organic chemical vapor deposition MOCVD reaction chamber, bake the substrate for 20 minutes at 1100°C and feed nitrogen gas, and then use a mixed carrier gas of nitrogen and ammonia for nitriding The temperature of the substrate is also 1100° C. for 3 minutes, as shown in FIG. 2 .

It should be noted that the sapphire substrate is used in this embodiment, and other substrates, such as silicon or silicon carbide, can also be used as long as the lattice matching degree with the non-polar A-plane GaN is less than 20%.

Step B: growing a non-polar A-side InGaN flexible layer on the substrate by using MOCVD technology;

Lower the substrate temperature after nitriding to 750°C, feed trimethylindium, trimethylgallium and ammonia gas into the reaction chamber as the reaction source, nitrogen as the carrier gas, and keep the pressure of the reaction chamber at 200torr Next, grow the A-side InGaN flexible layer.

The growth time of the non-polar A-side InGaN flexible layer is 2 to 16 minutes. The thickness of the non-polar A-side InGaN flexible layer is between 10 and 90 nm.

Step C: using MOCVD technology to grow a non-polar A-plane GaN buffer layer;

Lower the temperature of the substrate on which the InGaN flexible layer has been grown to 550°C, feed trimethylgallium and nitrogen into the reaction chamber as the reaction source, nitrogen as the carrier gas, and grow non-polar Low-temperature GaN buffer layer on side A. The growth time of the non-polar A-plane low-temperature GaN buffer layer is 3 minutes, and the thickness of the non-polar A-plane low-temperature GaN buffer layer is between 30 and 50 nm.

Step D: performing high-temperature annealing on the non-polar A-plane InGaN flexible layer and the non-polar A-plane GaN buffer layer to form a self-assembled lateral epitaxial template;

Raise the temperature of the substrate on which the non-polar A-face InGaN flexible layer and the low-temperature GaN buffer layer have been grown to 1100°C, and keep the flow of nitrogen gas and the pressure of the reaction chamber constant, and anneal for 5 minutes to form a self-assembled nanoscale A lateral epitaxial template, wherein the annealing temperature is 1100° C., and the annealing time is 5 minutes.

Of course, the annealing parameters can also be adjusted according to the needs, but it needs to be met. The annealing temperature should be greater than 1000°C, the annealing environment should be nitrogen environment or other inert gas environment, the pressure should be greater than 30torr, and the annealing time should be greater than 3 minutes.

Step E, using MOCVD technology to pass the gallium source and the nitrogen source into the reaction chamber with a carrier gas, and grow a non-polar A-plane GaN film on the lateral epitaxial template;

Keep the temperature of the self-assembled nanoscale lateral epitaxial template at 1100°C, feed gallium source and nitrogen gas into the reaction chamber as the reaction source, pure nitrogen or nitrogen/hydrogen moderate gas as the carrier gas, and keep the reaction chamber pressure at 50torr Growth of high-quality non-polar GaN thin films.

Step F, turn off the gallium source, turn off the ammonia gas when the reaction chamber drops below 300°C, and continue to feed the ammonia gas to inhibit the high-temperature thermal decomposition of the GaN material;

In step G, continue to lower the temperature. After the temperature of the reaction chamber drops from 300° C. to room temperature, the sample is taken out.

FIG. 2 is a schematic diagram of temperature changes during the process of preparing a non-polar A-plane GaN thin film according to an embodiment of the present invention. First, bake the substrate at 1100°C, nitriding it in an ammonia atmosphere for 3 minutes, then grow an InGaN film when the temperature drops to 750°C, and grow a low-temperature GaN buffer (LT) at 550°C for 3 minutes after the InGaN film is grown. GaN), and finally anneal the previously grown InGaN thin film and low-temperature GaN by using the heating time, and grow high-temperature GaN at 1100°C after 5 minutes, and take the slice after the growth is completed.

Fig. 3 is a schematic cross-sectional structure diagram of a non-polar A-plane GaN thin film prepared according to an embodiment of the present invention. As shown in Figure 3, InGaN and low-temperature GaN buffer layers are grown on the R-plane sapphire substrate with a thickness of 430 μm, and a self-assembled nanoscale lateral epitaxial template with a thickness of 30-120 nm is formed after annealing. For the purpose of the stress of the upper GaN film, a high-quality non-polar A-face GaN film of about 1 μm is grown on the lateral epitaxial template.

It should be noted that the non-polar A-side InGaN flexible layer, the non-polar A-side low-temperature GaN buffer layer and the non-polar A-side GaN film are all prepared by MOCVD. In fact, the three-layer film can also be prepared by other methods. Preparation methods, such as: electron beam evaporation, chemical vapor deposition, magnetron sputtering, etc., should also be included in the protection scope of the present invention.

FIG. 4 is an SEM image of a non-polar A-plane GaN thin film prepared by a conventional two-step method (A) and by the method (B) shown in FIG. 1 . As shown in Figure 4, for the sample (A) grown by the conventional method, the surface of the film is rough, which is a typical island-like growth mode, and the surface morphology of the film has not been improved with the increase of the thickness. The surface of the sample (B) grown by this technology shows a good trend of flattening of the film, and the surface morphology becomes relatively flat when the film thickness reaches 1um, indicating that the film islands have all merged to achieve two-dimensional growth .

FIG. 5 is a graph showing the variation of the rocking half-width with the azimuth angle of the non-polar A-plane GaN film prepared by the conventional two-step method and the method shown in FIG. 1 . As shown in Figure 5, the FWHM value is the smallest when the azimuth angle is 0°, and is the largest when the azimuth angle is 90°, showing obvious anisotropy. The FWHM of the sample (B) grown by the method of the present invention is obviously smaller than that of the sample (A) grown by the traditional process. This shows that our process can greatly improve the crystal quality of the film.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (12)

1. a method for preparing the non polarity A face GaN film is characterized in that, comprising:

Growing nonpolar A face InGaN flexible layer on substrate;

At said non polarity A side InGaN flexible layer growing nonpolar A face GaN resilient coating;

Said non polarity A side InGaN flexible layer and non polarity A side GaN resilient coating are annealed, form self assembly horizontal extension template; And

Growing nonpolar A face GaN film on said self assembly horizontal extension template.

2. the method for preparing the non polarity A face GaN film according to claim 1 is characterized in that, in the said step that non polarity A side InGaN flexible layer and non polarity A side GaN resilient coating are annealed: annealing temperature is greater than 1000 ℃; Environment is nitrogen environment or inert gas environment; Annealing time was greater than 3 minutes.

3. the method for preparing the non polarity A face GaN film according to claim 2 is characterized in that, annealing temperature is 1100 ℃; Environment is a nitrogen environment, and pressure is 50torr; Annealing time is 5 minutes.

4. the method for preparing the non polarity A face GaN film according to claim 1 is characterized in that, adopts the metal-organic chemical vapor deposition equipment mocvd method said non polarity A side GaN resilient coating of growing.

5. the method for preparing the non polarity A face GaN film according to claim 4 is characterized in that, in the step of said employing mocvd method growing nonpolar A face GaN resilient coating: reaction source is trimethyl gallium and nitrogen; Carrier gas is a nitrogen.

6. the method for preparing the non polarity A face GaN film according to claim 4 is characterized in that, in the step of said employing mocvd method growing nonpolar A face GaN resilient coating: growth temperature is 550 ℃; Reative cell pressure 50torr; Growth time is 3 minutes.

7. the method for preparing the non polarity A face GaN film according to claim 1 is characterized in that, adopts the mocvd method said non polarity A side InGaN flexible layer of growing.

8. the method for preparing the non polarity A face GaN film according to claim 7 is characterized in that, in the step of said employing mocvd method growing nonpolar A face InGaN flexible layer: reaction source is trimethyl indium, trimethyl gallium and ammonia, and carrier gas is a nitrogen.

9. the method for preparing the non polarity A face GaN film according to claim 8 is characterized in that, in the step of said employing mocvd method growing nonpolar A face InGaN flexible layer: growth temperature is 750 ℃; Environment is a nitrogen environment, and pressure is 200torr.

10. according to each described method for preparing the non polarity A face GaN film in the claim 1 to 9, it is characterized in that, saidly on substrate, also comprise before the step of growing nonpolar A face InGaN flexible layer:

Said substrate is carried out high-temperature ammonolysis to be handled.

11. the method for preparing the non polarity A face GaN film according to claim 10 is characterized in that, saidly substrate is carried out the high-temperature ammonolysis processed steps comprises:

At 1100 ℃, under the condition of feeding nitrogen substrate was toasted 20 minutes;

At 1100 ℃, under the condition of the mixed carrier gas of feeding nitrogen and ammonia substrate was toasted 3 minutes.

12., it is characterized in that said substrate is R surface sapphire, SiC or Si according to each described method for preparing the non polarity A face GaN film in the claim 1 to 9.

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