A method for preparing p-type beta-Ga2O3, beta-Ga2O3 prepared by the method and applications thereof

Abstract

The application relates to the field of semiconductor materials, in particular to a method for preparing p-type beta-Ga2O3, prepared beta-Ga2O3 and application thereof. The method comprises the following steps: rapidly cooling beta-Ga2O3 film to room temperature after treating the beta-Ga2O3 film to a preset value of oxygen vacancy concentration; then introducing N2O in a supercritical fluid state into the treated beta-Ga2O3 film; oxidizing the oxygen vacancy under the condition of 180-220 DEG C and greater than or equal to 7.26 MPa for 30-60 min; finally, annealing the oxidized beta-Ga2O3 film at a temperature of 550-650 DEG C for 30-60 min, and the p-type beta-Ga2O3 is obtained. The method is based on the supercritical fluid process of N2O to reduce the background carrier concentration of beta-Ga2O3 gallium oxide, improve the deep energy level gallium vacancy concentration and effective doping of nitrogen atoms, realize the intrinsic defect and valence band engineering regulation of beta-Ga2O3, and the prepared p-type beta-Ga2O3 can be applied to bipolar beta-Ga2O3-based power electronic devices and radio frequency devices.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials, specifically to a method for preparing p-type β-Ga2O3, the prepared β-Ga2O3, and its applications. Background Technology

[0002] With the rapid development of energy, information, rail transportation, electric vehicles and other fields, higher requirements are being placed on the performance of power semiconductor devices. High voltage resistance, low loss and high power devices have become the future development trend. Gallium oxide (β-Ga2O3), as a new generation of power semiconductor material, has a large bandgap and strong resistance to extreme environments, and is expected to play an extremely important role in the field of future power devices.

[0003] However, there are still many problems in promoting the industrialization of β-Ga2O3 power semiconductor devices, including the preparation of large-size, high-quality single crystals, the difficulty of heat dissipation due to low thermal conductivity, the difficulty of p-type doping of β-Ga2O3 leading to the lack of homogeneous pn junctions to suppress the peak electric field at the anode edge (such as field rings, junction termination extension, etc.) in β-Ga2O3 devices, and the difficulty in designing and implementing enhancement-type structures.

[0004] There are many reasons why p-type doping of β-Ga₂O₃ is difficult to achieve. Currently, methods such as magnetron sputtering metal / N doping, magnetron sputtering N and metal co-doping, process optimization, and GaN-based solid-solid phase transition in-situ doping have been used for p-type β-Ga₂O₃ doping research. However, these methods either suffer from low effective doping concentrations or cause lattice distortion. Therefore, further research is needed to better achieve p-type β-Ga₂O₃ doping. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a new method for achieving p-type β-Ga2O3 doping. This method is based on the supercritical fluid process of N2O to reduce the background carrier concentration of β-Ga2O3 gallium oxide, increase the concentration of deep-level gallium vacancies and the effective doping of nitrogen atoms, and realize the intrinsic defects and valence band engineering control of β-Ga2O3. The p-type β-Ga2O3 prepared can be applied to bipolar β-Ga2O3-based power electronic devices and radio frequency devices such as gallium oxide BJTs, PIN diodes and IGBT devices.

[0006] This invention achieves the above-mentioned technical objective through the following technical solution: This invention provides a method for preparing p-type β-Ga2O3, comprising the following steps: annealing a β-Ga2O3 thin film until the oxygen vacancy concentration reaches a preset value of 10. 18 ~10 20 cm -3 Then quickly cool to room temperature;

[0007] N2O in a supercritical fluid state was introduced into the treated β-Ga2O3 film and subjected to oxygen oxidation treatment at 180–220 °C and ≥7.26 MPa for 30–60 min.

[0008] The oxidized β-Ga2O3 film is annealed in an oxygen / air atmosphere at a temperature of 550–650 °C for 30–60 min to obtain the final product.

[0009] As a preferred embodiment, the method for treating the β-Ga2O3 film to achieve a preset oxygen vacancy concentration is as follows: annealing the β-Ga2O3 film under oxygen-deficient conditions at a temperature ≥700℃, and controlling the annealing temperature and annealing time to achieve the preset oxygen vacancy concentration.

[0010] As a preferred embodiment, the oxygen-deficient condition is that the oxygen volume percentage is ≤5%.

[0011] As a preferred embodiment, the oxygen volume ratio in the oxygen / air atmosphere is ≥20%.

[0012] As a preferred embodiment, the method for introducing supercritical fluid N2O into the treated β-Ga2O3 film is as follows: the β-Ga2O3 film is placed in an environment filled with supercritical fluid N2O.

[0013] In a preferred embodiment, the β-Ga₂O₃ film has a thickness of 10–20 μm, a surface roughness of <1 nm, and a surface defect density of <10. 4 cm -2 Fatal surface defects <10cm -2 Background carrier concentration > 10 16 cm -3 .

[0014] In a preferred embodiment, the β-Ga2O3 thin film is prepared by: obtaining a 20-30 μm thin film on a 2-4 inch β-Ga2O3 wafer using hydride vapor phase epitaxy, followed by chemical mechanical polishing.

[0015] In a preferred embodiment, the β-Ga2O3 wafer is prepared by a casting method.

[0016] The second objective of this invention is to protect the p-type β-Ga2O3 prepared by the above method.

[0017] The third objective of this invention is to protect the application of p-type β-Ga2O3 prepared by the above method in bipolar β-Ga2O3-based power electronic devices.

[0018] The method for preparing p-type β-Ga₂O₃ provided by this invention involves treating a gallium oxide thin film under oxygen-deficient conditions at ≥700℃ to introduce a large number of oxygen vacancies. Subsequently, a supercritical fluid N₂O source is diffused into the film by changing the pressure and temperature. Utilizing the strong oxidizing properties of N₂O, it forms Ga-N bonds with Ga atoms at the oxygen vacancies, thereby effectively heavy doping N (10⁻⁶). 18 ~10 19 cm 3 In the gallium oxide lattice. Due to N 2p Orbit and O 2p Orbital hybridization and orbital covalent properties lead to increased dispersion at the valence band top of gallium oxide thin films and reduced effective hole mass. Modulating the valence band engineering of gallium oxide reduces N0 at room temperature. O The ionization energy increases the effective hole concentration and hole mobility. Subsequently, gallium oxide is annealed in an oxygen / air atmosphere. Due to the oxygen-rich environment, V... Ga The formation energy is reduced, thus generating a large amount of V. Ga Defects, compensate for shallow donor level impurities such as Si and deeply rooted principal level V O The defect was compensated for by background carrier concentration, resulting in a higher Ga vacancy concentration. Attached Figure Description

[0019] Figure 1 The flowchart for preparing p-type β-Ga2O3 according to the present invention;

[0020] Figure 2 This is a schematic diagram illustrating the process of preparing P-type β-Ga2O3 according to an embodiment of the present invention. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0022] Currently, co-doping with metals has been proven to be a potential approach for achieving p-type β-Ga2O3, but it has the following drawbacks: No defect formation energy is high regardless of magnetron sputtering or N-ion implantation, and only a portion of the doped N atoms can form N2O3. o Defects include low effective doping concentration; metal doping to replace Ga atoms also has the problem of high defect formation energy, resulting in low effective doping concentration of metal; excessive metal doping concentration will cause lattice distortion, affecting the electrical properties of β-Ga2O3 thin films; holes generated by metal doping are easily adsorbed by oxygen polarons, thus failing to achieve hole conductivity.

[0023] The method described in this application is based on N2O supercritical fluid technology to reduce the background carrier concentration of β-Ga2O3, increase the concentration of deep-level gallium vacancies, and effectively dope nitrogen atoms, thereby achieving intrinsic defect and valence band engineering control of β-Ga2O3. The specific method is as follows:

[0024] First, the β-Ga₂O₃ film is treated under argon / oxygen-deficient conditions to introduce a large number of oxygen vacancies. Then, the pressure and temperature are changed to diffuse a supercritical fluid N₂O source into the film. Due to the strong oxidizing properties of N₂O, it can form Ga-N bonds with Ga atoms at the oxygen vacancies, thereby effectively heavy doping N (10⁻⁶). 18 -10 19 cm -3 In the gallium oxide lattice, due to N 2p Orbit and O 2p Orbital hybridization and orbital covalent properties lead to increased dispersion at the valence band apex and decreased effective hole mass. Modulating gallium oxide valence band engineering reduces N₂ at room temperature. O The ionization energy increases the effective hole concentration and hole mobility. Subsequently, gallium oxide is annealed in an oxygen / air atmosphere. Due to the oxygen-rich environment, V... Ga The formation energy is reduced, thus generating a large amount of V. Ga Defects, compensate for shallow donor level impurities such as Si and deeply rooted principal level V O The defect was compensated for by background carrier concentration, resulting in a higher Ga vacancy concentration.

[0025] The method for treating the β-Ga2O3 thin film until the oxygen vacancy concentration reaches a preset value is as follows: the crystal defect concentration can be controlled by temperature. Where N sites K represents the concentration of sites that can form defects. B Here, E is Boltzmann's constant, T is Kelvin temperature, and E is... f This is the energy for defect formation.

[0026] Under oxygen-rich conditions, the formation energies of the three types of oxygen vacancy defects in gallium oxide thin films are E f V OI = 3.31 eV, E f V OII =2.70eV, E f V OIII =3.57Ev; Under oxygen-deficient conditions, the formation of the three types of oxygen vacancies decreases. Therefore, β-Ga2O3 films are annealed under argon / oxygen-deficient conditions at temperatures ≥700℃. The annealing temperature and time are controlled to anneal until the oxygen vacancy concentration reaches the preset value (10). 18 -10 20 cm -3 ).

[0027] In this patent, the strong oxidizing power of N₂O is used to oxidize the gallium dangling bonds at oxygen vacancies in gallium oxide thin films, and the oxidation time is controlled to achieve heavy N doping. Furthermore, in an oxygen-rich environment, Ga vacancies are easily formed, compensating for donor impurities and reducing carrier concentration.

[0028] The unintentionally doped β-Ga2O3 thin films used in the examples were prepared by the following method: 20–30 μm thick β-Ga2O3 films were obtained on 2–4 inch β-Ga2O3 wafers prepared by efface casting (EFG) using hydride vapor phase epitaxy (HVPE). These β-Ga2O3 films were then polished to a thickness of 10 μm using chemical mechanical polishing (CMP) to obtain a thickness of 10–20 μm, a surface roughness <1 nm, and a surface defect density <10. 4 cm -2 Fatal surface defects <10cm -2 Background carrier concentration > 10 16 cm -3 β-Ga2O3 thin film.

[0029] N₂O has a supercritical temperature of 36.5°C and a critical pressure of 7.26 MPa. It belongs to a special phase of matter, with high permeability like a gas and high solubility like a liquid, and has almost no surface tension.

[0030] The following two specific embodiments will be used for detailed description. These embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention. Based on the specific embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0031] Example 1

[0032] This embodiment provides a method for preparing p-type β-Ga2O3, the specific steps of which are as follows:

[0033] S1. Place the β-Ga2O3 film into a sealed equipment chamber and anneal it for 60 minutes in an argon / oxygen-deficient atmosphere with an oxygen volume ratio of 5% at 700°C. This will diffuse oxygen atoms from the β-Ga2O3 lattice and form oxygen vacancies V0. The defect formation energy of V0 is reduced in the oxygen-deficient environment. After the annealing process, the β-Ga2O3 film is taken out and rapidly cooled to room temperature, which can "freeze" the oxygen vacancies generated at high temperature.

[0034] The concentration of oxygen vacancy defects was determined to be within 10 using XPS and Raman spectroscopy. 18 ~10 20 between;

[0035] S2, N2O is converted into a supercritical fluid state and introduced into a sealed chamber containing a β-Ga2O3 thin film, and treated at 200℃ and ≥7.26MPa for 60min to oxidize the gallium dangling bonds at oxygen vacancies;

[0036] S3, heat to 600℃ and anneal in air atmosphere (oxygen volume percentage 20.9%) for 60 minutes;

[0037] S4, after cooling, is taken out and obtained.

[0038] Example 2

[0039] This embodiment provides a method for preparing p-type β-Ga2O3, the specific steps of which are as follows:

[0040] S1. Place the β-Ga2O3 film into a sealed equipment chamber and anneal it for 60 minutes in an argon / oxygen-deficient atmosphere with an oxygen volume ratio of 3% at 800°C. This will diffuse oxygen atoms from the β-Ga2O3 lattice and form oxygen vacancies V0. The defect formation energy of V0 is reduced in the oxygen-deficient environment. After the annealing process, the β-Ga2O3 film is taken out and rapidly cooled to room temperature, which can "freeze" the oxygen vacancies generated at high temperature.

[0041] The concentration of oxygen vacancy defects was determined to be within 10 using XPS and Raman spectroscopy. 18 ~10 20 between;

[0042] S2, N2O is converted into a supercritical fluid state and introduced into a sealed chamber containing a β-Ga2O3 thin film, and treated at 210℃ and ≥7.26MPa for 40min to oxidize the gallium dangling bonds at oxygen vacancies;

[0043] S3, heat to 620℃ and anneal in air atmosphere (oxygen volume percentage 20.9%) for 40 minutes;

[0044] S4, after cooling, is taken out and obtained.

[0045] It should be noted that the above embodiments are only for further elaboration and explanation of the technical solution of the present invention, and are not intended to further limit the technical solution of the present invention. The method of the present invention is only a preferred embodiment and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing p-type β-Ga2O3, characterized in that, Includes the following steps: The β-Ga2O3 thin film was annealed until the oxygen vacancy concentration reached a preset value of 10. 18 ~10 20 cm -3 Then quickly cool to room temperature; N2O in a supercritical fluid state was introduced into the treated β-Ga2O3 film and oxidized at 180~220℃ and ≥7.26MPa for 30~60min. The oxidized β-Ga2O3 film is annealed in an oxygen / air atmosphere at a temperature of 550~650℃ for 30~60min to obtain the final product.

2. The method for preparing p-type β-Ga2O3 according to claim 1, characterized in that, The method for treating β-Ga2O3 films to achieve a preset oxygen vacancy concentration is as follows: annealing the β-Ga2O3 film under oxygen-deficient conditions at a temperature ≥700℃, and controlling the annealing temperature and annealing time until the oxygen vacancy concentration reaches the preset value.

3. The method for preparing p-type β-Ga2O3 according to claim 2, characterized in that, The hypoxic condition is when the oxygen volume percentage is ≤5%.

4. The method for preparing p-type β-Ga2O3 according to claim 1, characterized in that, The oxygen volume percentage in the air is ≥20%.

5. The method for preparing p-type β-Ga2O3 according to claim 1, characterized in that, The method for introducing supercritical fluid N2O into the treated β-Ga2O3 film is as follows: the β-Ga2O3 film is placed in an environment filled with supercritical fluid N2O.

6. The method for preparing p-type β-Ga2O3 according to claim 1, characterized in that, The β-Ga2O3 thin film has a thickness of 10~20 μm, a surface roughness of <1 nm, and a surface defect density of <10. 4 cm -2 Fatal surface defects <10cm -2 Background carrier concentration > 10 16 cm -3 .

7. The method for preparing p-type β-Ga2O3 according to claim 6, characterized in that, The β-Ga2O3 thin film is prepared by: obtaining a 20-30 μm thin film on a 2-4 inch β-Ga2O3 wafer using hydride vapor phase epitaxy, followed by chemical mechanical polishing.

8. The method for preparing p-type β-Ga2O3 according to claim 7, characterized in that, The β-Ga2O3 wafer was prepared by a casting method.

9. p-type β-Ga2O3 prepared by the method according to any one of claims 1 to 8.

10. The application of the p-type β-Ga2O3 according to claim 9 in bipolar β-Ga2O3-based power electronic devices.

Images