Beta-phase gallium oxide epitaxial layer and preparation method and application thereof

Abstract

The invention discloses a beta-phase gallium oxide epitaxial layer and a preparation method and application thereof. The preparation method comprises the following steps: growing a low-rate gallium oxide buffer layer on a substrate at a rate of 0.5-1 [mu] m / h by using a halide vapor phase epitaxy method, then growing a kappa-phase gallium oxide buffer layer on the low-rate gallium oxide buffer layer, and then converting kappa-phase gallium oxide into beta-phase gallium oxide by raising the temperature of the substrate, and growing a beta-phase gallium oxide epitaxial layer on the kappa-phase gallium oxide buffer layer. According to the preparation method, a halide vapor phase epitaxy method is used, kappa-Ga2O3 grown at a low temperature is used as a buffer layer, and a high-quality beta-phase gallium oxide epitaxial layer is grown on the buffer layer, so that the twin crystal orientation and defect density can be effectively reduced, the crystal quality and uniformity are improved, and a new idea is provided for epitaxial growth of a large-size gallium oxide material.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor material thin film epitaxy, and in particular to a β-phase gallium oxide epitaxial layer and a preparation method and application thereof. Background Art

[0002] Gallium oxide (Ga2O3) is an emerging ultra-wide bandgap semiconductor material with many excellent properties. Its bandgap width is as high as 4.9eV, which is much higher than semiconductor materials such as silicon carbide (3.26eV) and gallium nitride (3.4eV). In addition, gallium oxide also has extremely high breakdown electric field strength and extremely low on-resistance, which can reduce energy loss and improve power conversion efficiency. Epitaxial technology is the key to achieving high-quality gallium oxide film growth. Growing large-size, high-quality Ga2O3 epitaxial films is a prerequisite for mass production of high-performance devices. Compared with other epitaxial methods such as metal organic chemical vapor epitaxy (MOCVD), molecular beam epitaxy (MBE), pulsed laser deposition (PLD), etc., the halide vapor phase epitaxy (HVPE) method is a process method that is conducive to Ga2O3 epitaxy due to its high rate, large area, and stable film formation.

[0003] Due to its best thermal stability, β-Ga2O3 has become the most popular isomer of gallium oxide. However, due to the monoclinic structure of β-Ga2O3 and the large lattice mismatch between it and substrates such as sapphire, twin structures and a large number of defects are often formed during the epitaxial process, resulting in poor crystal quality of β-Ga2O3 epitaxial films.

[0004] In comparison, κ-phase Ga2O3 is a metastable gallium oxide isomer. Although its thermal stability is not as good as that of β-phase, it has a lower lattice mismatch with substrates such as sapphire and a lower growth temperature. In addition, κ-Ga2O3 can be transformed into β-Ga2O3 after being heated to a certain temperature. Therefore, using κ-Ga2O3 as a buffer layer, high-quality β-Ga2O3 epitaxial layers can be grown. Summary of the invention

[0005] In order to solve the deficiencies of the above technical solutions, the object of the present invention is to provide a β-phase gallium oxide epitaxial layer and a preparation method and application thereof.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A method for preparing a β-phase gallium oxide epitaxial layer comprises the following steps: utilizing a halide vapor phase epitaxy method to first grow a low-rate gallium oxide buffer layer at a rate of 0.5 to 1 μm / h on a substrate, then growing a κ-phase gallium oxide buffer layer on the low-rate gallium oxide buffer layer, then increasing the substrate temperature to convert the κ-phase gallium oxide into β-phase gallium oxide, and then growing a β-phase gallium oxide epitaxial layer on the κ-phase gallium oxide buffer layer.

[0008] In the above technical solution, the preparation method specifically comprises the following steps:

[0009] Step 1, after pre-treating the substrate, place it in the growth temperature zone of the halide vapor phase epitaxy equipment, use metal gallium as a reaction source and place it in the gallium source temperature zone, evacuate the chamber of the equipment and all pipelines of the equipment in turn, close the reaction gas line, and let the carrier gas line pass through the carrier gas nitrogen to flush the chamber of the equipment, and then adjust the carrier gas nitrogen flow rate to 500-800sccm;

[0010] Step 2, heating the gallium source temperature zone and the growth temperature zone in stages respectively. When the gallium source temperature zone is heated to 600° C. to 900° C. and the growth temperature zone is heated to 600° C. to 800° C., the temperature is kept constant, the flow rate of the carrier gas nitrogen is increased to 800 to 1000 sccm, and the reaction pressure and rotation speed of the equipment are set;

[0011] Step 3, continue to increase the flow rate of carrier gas nitrogen to 1000-1500 sccm, open the reaction gas path, introduce 200-500 sccm of oxygen, and introduce 5-20 sccm of HCl into the gallium source temperature zone, set the time to 5-20 minutes, and grow a low-rate gallium oxide buffer layer;

[0012] Step 4, increasing the flow rate of nitrogen carrier gas in the gallium source temperature zone to 1800-2500 sccm, increasing the flow rate of HCl to 20-50 sccm, increasing the flow rate of oxygen to 500-1000 sccm, and growing a κ-phase gallium oxide buffer layer on the low-rate gallium oxide buffer layer for a growth time of 10-30 minutes;

[0013] Step 5, keep the temperature of the gallium source temperature zone unchanged, and keep the flow rate of HCl and oxygen unchanged, or stop passing HCl and oxygen, and gradually increase the substrate temperature. When the substrate temperature rises to 900-1100°C, pass HCl with a flow rate of 20-50sccm and oxygen with a flow rate of 500-1000sccm to grow a β-phase gallium oxide epitaxial layer.

[0014] In the above technical solution, the substrate is a sapphire substrate.

[0015] In the above technical solution, in step 1, the substrate is pretreated by ultrasonically cleaning the substrate with anhydrous ethanol and acetone in sequence, and then taking out the substrate and rinsing it with deionized water and drying it.

[0016] In the above technical solution, in step 1, all pipeline switches are closed, and the chamber vacuum of the equipment is extracted for 10 to 20 minutes, and all pipeline switches are opened, and the pipeline vacuum is extracted for 3 to 5 minutes.

[0017] In the above technical solution, in step 1, 500 to 1000 sccm of carrier gas nitrogen is introduced to flush the chamber of the equipment for 5 to 10 minutes.

[0018] In the above technical solution, in step 2, the staged heating is as follows: the first stage: heating at 5 to 10°C per minute to 50 to 500°C; the second stage: heating at 5 to 10°C per minute to 500 to 800°C; the third stage: heating at 3 to 5°C per minute to 800 to 900°C.

[0019] In the above technical solution, in step 2, the reaction pressure is 50 to 90 kPa, and the rotation speed is 1 to 20 r / min.

[0020] In the above technical solution, the growth rate of the β-phase gallium oxide epitaxial layer is 5-20 μm / h, the thickness is 15-30 μm, and the thickness distribution is ≤±10%.

[0021] Another aspect of the present invention also includes a β-phase gallium oxide epitaxial layer obtained by the above preparation method.

[0022] Another aspect of the present invention also includes the application of the β-phase gallium oxide epitaxial layer in gallium oxide-based power devices.

[0023] The advantages and beneficial effects of the present invention are:

[0024] 1. The preparation method of the present invention uses halide vapor phase epitaxy and utilizes κ-Ga2O3 grown at a relatively low temperature as a buffer layer, on which a high-quality β-phase gallium oxide epitaxial layer is grown, which can effectively reduce the twin orientation and defect density, improve the crystal quality and uniformity, and provide a new idea for the epitaxial growth of large-size gallium oxide materials.

[0025] 2. The growth rate of the β-phase gallium oxide epitaxial layer prepared by the preparation method of the present invention reaches 5-20 μm / h, the thickness can reach 15-30 μm, and the thickness distribution is ≤±10%; the β-phase gallium oxide epitaxial layer shows good high crystal quality and uniformity, XRD

[0026] The —θ-2θ scanning results show a strong diffraction peak and its secondary diffraction peak in the β-Ga2O3 (201) orientation, indicating that gallium oxide grows along a single orientation. The half-width at half maximum of the rocking curve is 1663 arcsec. The scanning electron microscope results show that the β-phase gallium oxide epitaxial layer has a uniform thickness and a smooth surface. The β-phase gallium oxide epitaxial layer (epitaxial film) of the present invention provides strong support for the research and development of high-performance Ga2O3-based power devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A diagram of a growth system of a β-phase gallium oxide epitaxial layer using a halide vapor phase epitaxy method according to Example 1 of the present invention;

[0028] Figure 2 This is a schematic diagram of the structural layers of Example 1 of the present invention;

[0029] Figure 3 This is a cross-sectional SEM image of the κ-phase gallium oxide buffer layer of Example 1 of the present invention;

[0030] Figure 4 This is a surface SEM image of the κ-phase gallium oxide buffer layer of Example 1 of the present invention;

[0031] Figure 5 This is an XRD θ-2θ scanning diagram of the κ-phase gallium oxide buffer layer of Example 1 of the present invention;

[0032] Figure 6 is a rocking curve diagram of the κ-phase gallium oxide buffer layer of Example 1 of the present invention;

[0033] Figure 7 This is a cross-sectional SEM image of a β-phase gallium oxide epitaxial layer of Example 1 of the present invention;

[0034] Figure 8 This is a surface SEM image of the β-phase gallium oxide epitaxial layer of Example 1 of the present invention;

[0035] Fig. 9 This is an XRD θ-2θ scanning diagram of the β-phase gallium oxide epitaxial layer of Example 1 of the present invention;

[0036] Fig.10 is a rocking curve diagram of the β-phase gallium oxide epitaxial layer of Example 1 of the present invention;

[0037] Fig.11 This is a physical picture of the β-phase gallium oxide epitaxial layer of Example 1 of the present invention;

[0038] Fig.12 It is a schematic diagram of the structural layer of Comparative Example 1;

[0039] Fig.13 This is a cross-sectional SEM image of the β-Ga2O3 epitaxial layer of Comparative Example 1;

[0040] Fig.14 This is the surface SEM image of the β-Ga2O3 epitaxial layer of Comparative Example 1;

[0041] Fig.15 It is the XRDθ-2θ scanning diagram of the β-Ga2O3 epitaxial layer of Comparative Example 1;

[0042] Fig.16 This is the actual β-Ga2O3 epitaxial layer of Comparative Example 1. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0044] Example 1

[0045] A method for preparing a β-phase gallium oxide epitaxial layer comprises the following steps:

[0046] like Figure 1-Figure 2 As shown, step 1, using c-plane sapphire as a substrate to grow a β-phase gallium oxide epitaxial layer, before the epitaxial work begins, the substrate is ultrasonically cleaned with anhydrous ethanol and acetone for 20 minutes in sequence, and after the substrate is taken out, it is rinsed with deionized water and blown dry with a nitrogen gun, and then fixed on a ceramic tray. The ceramic tray is fixed on a base using a graphite rod and placed in a growth temperature zone (reaction temperature zone) of a halide vapor phase epitaxy device. Metal gallium particles are placed in a quartz boat in the gallium source temperature zone as a reaction source, and all pipelines in the device are closed. The chamber in the device (the growth temperature zone and the gallium source temperature zone are set in the chamber) is evacuated for 10 minutes, and all pipelines are opened to evacuate for 3 minutes, and then the reaction gas path is closed. A carrier gas nitrogen with a flow rate of 500 sccm is introduced into the carrier gas path to flush the chamber for 5 minutes, and then the carrier gas nitrogen is adjusted to 600 sccm.

[0047] Step 2, heat the gallium source temperature zone and the growth temperature zone in stages. When the gallium source temperature zone is heated to 750°C and the growth temperature zone is heated to 600°C, keep the temperature unchanged for 30 minutes, increase the carrier gas nitrogen flow rate to 800sccm, set the reaction pressure to 80kPa, start rotation, and the rotation speed is 5r / min.

[0048] Step 3, continue to increase the carrier gas nitrogen flow rate to 1000 sccm, open the reaction gas path for 5 to 20 minutes, introduce 300 sccm of oxygen, and introduce 5 sccm of HCl into the gallium source temperature zone to grow a gallium oxide buffer layer at a low rate.

[0049] Step 4, increase the flow rate of carrier gas nitrogen to 2000 sccm, increase the flow rate of HCl to 30 sccm, increase the flow rate of oxygen to 800 sccm, and grow a κ-phase gallium oxide buffer layer on the low-rate gallium oxide buffer layer for 10 minutes.

[0050] Step 5, keep the temperature of the gallium source temperature zone unchanged, and keep the flow rate of HCl and oxygen unchanged, or stop the flow of HCl and oxygen, and gradually increase the substrate temperature. When the substrate temperature rises to 1100°C, introduce HCl with a flow rate of 30sccm and oxygen with a flow rate of 500sccm. The growth time is 3 hours to grow a β-phase gallium oxide epitaxial layer.

[0051] Step 6, close the oxygen and HCl gas lines in turn, return the pressure to zero, adjust the carrier gas nitrogen flow rate to 1000sccm, purge for 1 hour, return the carrier gas nitrogen flow rate to zero, close all gas lines, turn off the rotation, cool down for 20 hours until the chamber temperature drops to 50°C, turn off the mechanical pump and main pumping valve of the equipment, open the carrier gas line, pass the carrier gas nitrogen until the inside of the equipment reaches atmospheric pressure, then take out the sample to obtain a β-phase gallium oxide epitaxial layer with sapphire as the substrate.

[0052] Figure 3-Figure 4 The cross-section and surface SEM images of the κ-phase gallium oxide buffer layer in Example 1 show that the surface of the κ-phase gallium oxide buffer layer is flat, the thickness is 2.08 μm, and the distribution is uniform.

[0053] Figure 5-Figure 6 : is the XRD pattern of the κ-phase gallium oxide buffer layer of Example 1. The κ-phase gallium oxide buffer layer grows along a single κ-Ga2O3 (001) orientation, and the half-height width of the rocking curve is only 379 arcsec.

[0054] Figure 7-Figure 8 The SEM cross-section and surface images of the β-phase gallium oxide epitaxial layer of Example 1 show that the thickness of the β-phase gallium oxide epitaxial layer reaches 20.83 μm, and the surface is still uniform and flat.

[0055] Figure 9-10 This is the XRD diagram of the β-phase gallium oxide epitaxial layer of Example 1. It can be seen from the figure that: The crystal plane and its secondary diffraction peaks, and the absence of gallium oxide diffraction peaks in other crystal directions, indicate that the β-phase gallium oxide epitaxial layer grows along a single orientation. The half-width at half maximum of the rocking curve is 1663 arcsec, and a β-phase gallium oxide epitaxial layer with good crystal quality is obtained.

[0056] Depend on Fig.11 It can be seen that the β-phase gallium oxide epitaxial layer has a flat and uniform surface and high transparency.

[0057] Comparative Example 1

[0058] A method for preparing a β-Ga2O3 epitaxial layer comprises the following steps:

[0059] like Figure 1 / Fig.12As shown, step 1, c-plane sapphire is used as a substrate to grow a β-Ga2O3 epitaxial layer. Before the epitaxial work begins, the substrate is ultrasonically cleaned with anhydrous ethanol and acetone for 20 minutes in sequence. After the substrate is taken out, it is rinsed with deionized water and blown dry with a nitrogen gun, and then fixed on a ceramic tray. The ceramic tray is fixed on a base with a graphite rod and placed in a growth temperature zone (reaction temperature zone) of a halide vapor phase epitaxy device. Metal gallium particles are placed in a quartz boat in the gallium source temperature zone as a reaction source, and all pipelines in the device are closed. The chamber in the device (the growth temperature zone and the gallium source temperature zone are set in the chamber) is evacuated for 10 minutes. After opening all pipelines and evacuating for 3 minutes, the reaction gas path is closed, and a carrier gas nitrogen with a flow rate of 500sccm is introduced into the carrier gas path to flush the chamber for 5 minutes, and then the carrier gas nitrogen is adjusted to 600sccm.

[0060] Step 2, heat the gallium source temperature zone and the growth temperature zone in stages respectively. When the gallium source temperature zone is heated to 750°C and the growth temperature zone is heated to 1100°C, keep the temperature unchanged for 30 minutes, increase the carrier gas nitrogen flow rate to 800sccm, set the reaction pressure to 80kPa, start rotation, and the rotation speed is 5r / min.

[0061] Step 3, continue to increase the carrier gas nitrogen flow rate to 1000 sccm, open the reaction gas path for 5 to 20 minutes, introduce 300 sccm of oxygen, and introduce 5 sccm of HCl into the gallium source temperature zone to grow a gallium oxide buffer layer at a low rate.

[0062] Step 4, increase the flow rate of carrier gas nitrogen to 2000 sccm, increase the flow rate of HCl to 30 sccm, keep the oxygen flow rate unchanged at 500 sccm, and grow the β-Ga2O3 epitaxial layer for 1 hour.

[0063] Step 5, close the oxygen and HCl gas lines in turn, return the pressure to zero, adjust the carrier gas nitrogen flow rate to 1000sccm, purge for 1 hour, return the carrier gas nitrogen flow rate to zero, close all gas lines, turn off the rotation, cool down for 20 hours until the chamber temperature drops to 50°C, turn off the mechanical pump and main pumping valve of the equipment, open the carrier gas line, introduce carrier gas nitrogen until the inside of the equipment reaches atmospheric pressure, then take out the sample to obtain a β-Ga2O3 epitaxial layer with sapphire as the substrate.

[0064] Depend on Figure 13-14 It can be seen that the surface of the β-Ga2O3 epitaxial layer obtained in Comparative Example 1 without using κ-phase gallium oxide as a buffer layer is rough, the β-Ga2O3 epitaxial layer is not tightly bonded to the substrate, there are gaps, and the thickness distribution is uneven.

[0065] Depend on Fig.15 It can be seen that the XRD diffraction peak of the β-Ga2O3 epitaxial layer obtained in Comparative Example 1 without using κ-phase gallium oxide as a buffer layer is weak and the crystal quality is poor.

[0066] Depend on Fig.16 It can be seen that the surface of the β-Ga2O3 epitaxial layer is rough and whitish, and its transparency is low.

[0067] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for preparing a β-phase gallium oxide epitaxial layer, characterized in that: Using the halide vapor phase epitaxy method, a low-rate gallium oxide buffer layer is first grown on the substrate at a rate of 0.5 to 1 μm / h, and then a κ-phase gallium oxide buffer layer is grown on the low-rate gallium oxide buffer layer. Then, the κ-phase gallium oxide is converted into β-phase gallium oxide by increasing the substrate temperature, and a β-phase gallium oxide epitaxial layer is grown on the κ-phase gallium oxide buffer layer.

2. The preparation method according to claim 1, characterized in that: The specific steps include: Step 1, after pre-treating the substrate, place it in the growth temperature zone of the halide vapor phase epitaxy equipment, use metal gallium as a reaction source and place it in the gallium source temperature zone, evacuate the chamber of the equipment and all pipelines of the equipment in turn, close the reaction gas line, and let the carrier gas line pass through the carrier gas nitrogen to flush the chamber of the equipment, and then adjust the carrier gas nitrogen flow rate to 500-800sccm; Step 2, heating the gallium source temperature zone and the growth temperature zone in stages respectively. When the gallium source temperature zone is heated to 600° C. to 900° C. and the growth temperature zone is heated to 600° C. to 800° C., the temperature is kept constant, the flow rate of the carrier gas nitrogen is increased to 800 to 1000 sccm, and the reaction pressure and rotation speed of the equipment are set; Step 3, continue to increase the flow rate of carrier gas nitrogen to 1000-1500 sccm, open the reaction gas path, introduce 200-500 sccm of oxygen, and introduce 5-20 sccm of HCl into the gallium source temperature zone, set the time to 5-20 minutes, and grow a low-rate gallium oxide buffer layer; Step 4, increasing the flow rate of nitrogen carrier gas in the gallium source temperature zone to 1800-2500 sccm, increasing the flow rate of HCl to 20-50 sccm, increasing the flow rate of oxygen to 500-1000 sccm, and growing a κ-phase gallium oxide buffer layer on the low-rate gallium oxide buffer layer for a growth time of 10-30 minutes; Step 5, keep the temperature of the gallium source temperature zone unchanged, and keep the flow rate of HCl and oxygen unchanged, or stop passing HCl and oxygen, and gradually increase the substrate temperature. When the substrate temperature rises to 900-1100°C, pass HCl with a flow rate of 20-50sccm and oxygen with a flow rate of 500-1000sccm to grow a β-phase gallium oxide epitaxial layer.

3. The preparation method according to claim 1, characterized in that: In the step 1, the substrate is a sapphire substrate, and the substrate pretreatment is to ultrasonically clean the substrate with anhydrous ethanol and acetone in sequence, and then rinse the substrate with deionized water and blow dry it.

4. The preparation method according to claim 1, characterized in that: In the step 1, all pipeline switches are closed, and the chamber of the equipment is vacuumed for 10 to 20 minutes, and all pipeline switches are opened, and the pipelines are vacuumed for 3 to 5 minutes.

5. The preparation method according to claim 1, characterized in that: In the step 1, 500-1000 sccm of nitrogen as a carrier gas is introduced to flush the chamber of the equipment for 5-10 minutes.

6. The preparation method according to claim 1, characterized in that: In step 2, the temperature is increased in stages. In the first stage, the temperature is increased by 5 to 10°C per minute to 50 to 500°C; in the second stage, the temperature is increased by 5 to 10°C per minute to 500 to 800°C; in the third stage, the temperature is increased by 3 to 5°C per minute to 800 to 900°C.

7. The preparation method according to claim 1, characterized in that: In the step 2, the reaction pressure is 50 to 90 kPa, and the rotation speed is 1 to 20 r / min.

8. The preparation method according to claim 1, characterized in that: The growth rate of the β-phase gallium oxide epitaxial layer is 5-20 μm / h, the thickness is 15-30 μm, and the thickness distribution is ≤±10%. 9 . The β-phase gallium oxide epitaxial layer obtained by the preparation method according to claim 1 .

10. Use of the β-phase gallium oxide epitaxial layer according to claim 9 in a gallium oxide-based power device.

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