N-type high-carrier-concentration beta-Ga2O3 single crystal material as well as preparation method and application thereof
By combining the melt method with neutron irradiation and high-temperature activation treatment, the problem of preparing large-size, high-carrier-concentration β-Ga2O3 single crystals by the Czochralski method has been solved, achieving efficient and low-cost crystal preparation and improving crystal quality.
Patent Information
- Application Number
- CN202511219859.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-28
- Publication Date
- 2025-12-23
AI Technical Summary
The existing Czochralski method is difficult to prepare large-size β-Ga2O3 single crystal materials with high carrier concentration, resulting in decreased crystal quality and high production costs.
Low carrier concentration β-Ga2O3 single crystal materials were prepared by melt method. High carrier concentration β-Ga2O3 single crystal materials were prepared by controlling the doping concentration of germanium atoms through neutron irradiation treatment and high temperature activation treatment.
The preparation of large-size, high carrier concentration β-Ga2O3 single crystal materials has been achieved, solving the defects such as spiral growth, twinning and dislocation in the Czochralski method and reducing production costs.
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Figure CN121183431A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of gallium oxide semiconductor material technology, specifically relating to an n-type high carrier concentration β-Ga2O3 single crystal material, its preparation method, and its application. Background Technology
[0002] As a representative of fourth-generation semiconductors, gallium oxide (Ga2O3) shows promise as a preferred material for high-voltage, high-power, low-loss power devices and deep-ultraviolet optoelectronic devices due to its larger bandgap, higher breakdown voltage, greater Barry's figure of merit, and lower production cost compared to third-generation semiconductors. Gallium oxide single-crystal materials are a prerequisite and guarantee for subsequent thin-film epitaxy and device fabrication, and are fundamental to the application of semiconductor materials.
[0003] β-Ga₂O₃ single crystals are currently the only wide-bandgap semiconductor material that can be grown using the melt method, which helps reduce the production cost of gallium oxide. The melt method for preparing β-Ga₂O₃ single crystals mainly includes the Czochralski (CZ) method, the EFG method (an improved Czochralski method), and the Bridgman (BM) method. Among these, the Czochralski method has advantages such as fast crystal growth rate (1-3 cm / h, about 100 times that of silicon carbide), low production cost (one-third that of silicon carbide), and fewer crystal defects, and is widely used in first- and second-generation semiconductors.
[0004] However, β-Ga₂O₃ single crystals have poor thermal conductivity, only one-tenth that of silicon carbide and gallium nitride. During the Czochralski method for growing β-Ga₂O₃ single crystals, heat dissipation conditions and solid-liquid interface control have a significant impact on crystal growth. In in-situ doping techniques, Si... 4 + 、Ge 4+ and Sn 4+ As donor impurities, they enter the β-gallium oxide lattice, increasing the concentration of charge carriers (free electrons) and giving the crystal n-type conductivity. However, the increased electron concentration leads to increased infrared radiation absorption, causing an imbalance in the temperature gradient at the melt-crystal interface and resulting in irregular spiral growth defects. Furthermore, the Czochralski method and other melt methods can also produce defects such as twins and dislocations in highly doped gallium oxide single crystals, leading to a decrease in crystal quality.
[0005] Studies have shown that when the Czochralski method is used to prepare carriers with a concentration of 10... 18 / cm 3 When processing β-Ga₂O₃ single crystal materials, significant spiral growth occurs, while when the carrier concentration is controlled to be less than 10 using the Czochralski method... 16 / cm 3When processing β-Ga₂O₃ single crystal materials, the resulting single crystals have regular shapes, and spiral growth is effectively suppressed. Currently, it is impossible to prepare large-sized β-Ga₂O₃ single crystal materials with high carrier concentration (i.e., high doping concentration) using the Czochralski method.
[0006] The physical properties of gallium oxide prevent the Czochralski method from fabricating large-size, high-carrier-concentration doped β-Ga2O3 single crystals and substrates, thus hindering the realization of its advantages in high-efficiency and low-cost fabrication. Therefore, it is urgent to optimize and improve the Czochralski process, remove technical obstacles and bottlenecks, and promote the research and application of Czochralski technology in β-Ga2O3. Summary of the Invention
[0007] This application provides an n-type high carrier concentration β-Ga2O3 single crystal material, its preparation method and application, aiming to solve the problem that the existing Czochralski method cannot prepare high carrier concentration (i.e., high doping concentration) and large-size gallium oxide single crystal materials.
[0008] The first aspect of this application provides a method for preparing an n-type high carrier concentration β-Ga2O3 single crystal material, comprising the following steps:
[0009] (1) β-Ga2O3 single crystal material with low carrier concentration was prepared by melt method;
[0010] (2) Calculate the theoretical doping concentration of germanium atoms in β-Ga2O3 single crystal material; neutron irradiation treatment is performed on β-Ga2O3 single crystal material with low carrier concentration to obtain germanium-doped β-Ga2O3 single crystal material.
[0011] (3) The germanium-doped β-Ga2O3 single crystal material is activated to obtain the n-type high carrier concentration β-Ga2O3 single crystal material.
[0012] According to some embodiments of the preparation method of n-type high carrier concentration β-Ga2O3 single crystal material described in this application, in step (1), the carrier concentration of the low carrier concentration β-Ga2O3 single crystal material is ≤10. 16 / cm 3 .
[0013] According to some embodiments of the preparation method of the n-type high carrier concentration β-Ga2O3 single crystal material described in this application, the preparation method of the low carrier concentration β-Ga2O3 single crystal material includes one or more of the Czochralski method (CZ method), the EFG method, and the Bridgman method (BM method); as a preferred embodiment, the preparation method is the Czochralski method.
[0014] According to some embodiments of the preparation method of n-type high carrier concentration β-Ga2O3 single crystal material described in this application, the control method for preparing low carrier concentration β-Ga2O3 single crystal material by melt method includes unintentional doping or doping with acceptor impurities.
[0015] According to some embodiments of the preparation method of the n-type high carrier concentration β-Ga2O3 single crystal material described in this application, the acceptor impurity includes one or more of Fe, N and Mg.
[0016] According to some embodiments of the preparation method of n-type high carrier concentration β-Ga2O3 single crystal material described in this application, in step (2), the theoretical doping concentration of germanium atoms in the germanium-doped β-Ga2O3 single crystal material is calculated by the following formula:
[0017]
[0018] Where: N d This represents the theoretical doping concentration of germanium atoms, expressed in atoms / cm². 3 ;
[0019] N Ga The density of gallium atoms in β-Ga₂O₃ is 3.82 × 10⁻⁶. 22 atoms / cm 3 ;
[0020] f1 represents the abundance of the Ga-69 isotope in gallium oxide, with a value of 0.604.
[0021] f2 represents the abundance of the Ga-71 isotope in gallium oxide, with a value of 0.396.
[0022] ρ1 is the thermal neutron capture cross section of Ga-69, with a value of 1.68 × 10⁻⁶. -24 cm 2 ;
[0023] ρ2 is the thermal neutron capture cross section of Ga-71, with a value of 4.70 × 10⁻⁶. -24 cm 2 ;
[0024] ψ represents the neutron flux of the irradiated neutron source, expressed in n / (cm²). 2 ·s);
[0025] t is the reaction time of neutron irradiation, measured in seconds.
[0026] According to some embodiments of the preparation method of n-type high carrier concentration β-Ga2O3 single crystal material described in this application, in step (2), the neutron source for neutron irradiation treatment includes a reactor neutron source or an accelerator neutron source.
[0027] According to some embodiments of the preparation method of the n-type high carrier concentration β-Ga2O3 single crystal material described in this application, the neutron flux of the neutron source is 10. 12 -10 16 n / (cm 2 ·s).
[0028] According to some embodiments of the preparation method of n-type high carrier concentration β-Ga2O3 single crystal material described in this application, in step (3), the activation treatment includes high temperature activation and / or laser activation.
[0029] According to some embodiments of the preparation method of n-type high carrier concentration β-Ga2O3 single crystal material described in this application, the atmosphere of the activation treatment is an oxygen atmosphere.
[0030] According to some embodiments of the preparation method of the n-type high carrier concentration β-Ga2O3 single crystal material described in this application, the high-temperature activation temperature is 700-850℃, and the high-temperature activation time is 30-60min.
[0031] The second aspect of this application provides an n-type high carrier concentration β-Ga2O3 single crystal material, which is prepared by the preparation method described in the first aspect of this application.
[0032] According to some embodiments of the n-type high carrier concentration β-Ga2O3 single crystal material described in this application, the β-Ga2O3 single crystal material contains the dopant element germanium.
[0033] According to some embodiments of the n-type high carrier concentration β-Ga2O3 single crystal material described in this application, the carrier concentration of the β-Ga2O3 single crystal material is 10. 16 -5×10 20 / cm 3 The size of the β-Ga2O3 single crystal material is 50-300 mm.
[0034] According to some embodiments of the n-type high carrier concentration β-Ga2O3 single crystal material described in this application, the β-Ga2O3 single crystal material includes one or more of β-Ga2O3 single crystal ingots, β-Ga2O3 single crystal rods, β-Ga2O3 single crystal wafers, and β-Ga2O3 single crystal substrates.
[0035] The third aspect of this application provides an application of the n-type high carrier concentration β-Ga2O3 single crystal material described in the second aspect of this application in the field of wide bandgap semiconductor devices.
[0036] The beneficial effects of this application include: the carrier concentration of the n-type high carrier concentration β-Ga2O3 single crystal material described in this application is 10 16 -5×1020 / cm 3 The range is adjustable, with a size range of 50-300mm.
[0037] The n-type high carrier concentration β-Ga2O3 single crystal material described in this application employs a combination of melt method and neutron irradiation technology, which solves the defects such as spiral growth, twinning, and dislocations that exist in the preparation of large-size, high carrier concentration doped gallium oxide single crystal materials by the Czochralski method. This allows the high-efficiency preparation advantage of the Czochralski method to be brought into play, and it can be industrialized. This provides a feasible method for the preparation of low-cost n-type β-Ga2O3 single crystal substrates and their application in semiconductor power devices. Attached Figure Description
[0038] Figure 1 The figure shows the effect of different activation temperatures on the germanium doping concentration and carrier concentration of β-Ga2O3 wafers. Detailed Implementation
[0039] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.
[0040] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0041] This application provides a method for preparing n-type high carrier concentration β-Ga2O3 single crystal material, including the following steps:
[0042] (1) Low carrier concentration β-Ga2O3 single crystal material was prepared by melt method;
[0043] (2) Calculate the theoretical doping concentration of germanium atoms in β-Ga2O3 single crystal material; neutron irradiation treatment is performed on β-Ga2O3 single crystal material with low carrier concentration to obtain germanium-doped β-Ga2O3 single crystal material.
[0044] (3) The germanium-doped β-Ga2O3 single crystal material is activated to obtain the n-type high carrier concentration β-Ga2O3 single crystal material.
[0045] Since the dopants for n-type gallium oxide single crystals are mainly group IVA and IVB elements, including Si, Ge, Sn, Ti, and Zr, Ge doping can be achieved by adding dopants (such as GeH4) or by nuclear reactions between Ga atoms and neutrons. Addressing the limitation of existing Czochralski methods in preparing gallium oxide single crystals with high carrier concentrations (i.e., high doping concentrations), this application introduces neutron irradiation to achieve germanium doping of gallium oxide single crystals. By combining the Czochralski method with neutron irradiation, the technical problem of the inability of the Czochralski method to prepare large-size, high-carrier-concentration doped gallium oxide single crystals is solved.
[0046] This application is the first to study the mechanism of the neutron capture reaction between gallium oxide crystals and nuclear physics. The principle is as follows:
[0047] Gallium oxide contains Ga-69 isotopes (60.4% natural abundance) and Ga-71 isotopes (39.6% natural abundance), whose nuclei undergo neutron absorption and subsequent reactions. 69 Ga(n,γ) 70 Ga and 71 Ga(n,γ) 72 Ga nucleus reaction.
[0048] 69 Ga+n→ 70 Ga→ 70 Ge+βˉ+νˉ(T 1 / 2 =21.1m)(Reaction 1)
[0049] 71 Ga+n→ 72 Ga→ 72 Ge+βˉ+νˉ(T 1 / 2 =14.1h)(Reaction 2)
[0050] Through neutron capture reactions 1 and 2, Ga atoms in gallium oxide crystals are converted into Ge atoms.
[0051] After conversion, Ge atoms exhibit shallow donor impurity characteristics in gallium oxide crystals, resulting in low ionization energy. After activation treatment, one of their valence electrons absorbs energy and transitions to the conduction band, becoming a free charge carrier. Once germanium atoms are fully activated, the germanium impurity concentration in the crystal is approximately equal to the charge carrier concentration. Therefore, the charge carrier concentration in the crystal can be estimated by using the germanium doping concentration.
[0052] In some embodiments of this application, in step (1), the carrier concentration of the low carrier concentration β-Ga2O3 single crystal material is ≤10. 16 / cm 3 Because the carrier concentration of gallium oxide single crystal material is 10 16 / cm 3The following measures are necessary to prevent spiral growth in single crystals, ensuring that the grown single crystals have regular shapes, few defects, and high crystal quality.
[0053] In some embodiments of this application, the method for preparing β-Ga2O3 single crystal materials with low carrier concentration using the melt method includes one or more of the Czochralski (CZ) method, the EFG method, and the Bridgman (BM) method, with the Czochralski method being preferred. The process for preparing β-Ga2O3 single crystal materials with low carrier concentration using the Czochralski method mainly includes steps such as preparing the substrate, seeding, necking, shoulder reduction, and constant diameter growth.
[0054] In some embodiments of this application, the method for controlling the preparation of low carrier concentration β-Ga2O3 single crystal materials by melt method includes unintentional doping or doping with acceptor impurities; more preferably, the acceptor impurities include one or more of Fe, N, and Mg. Unintentional doping is a common practice in the industry, where no specific dopant is added, allowing trace impurities contained in the raw materials, crucible, carrier gas, and growth environment to naturally incorporate into the semiconductor crystal material during crystal growth. The deep-level acceptor impurities include Fe, N, and Mg, preferably Fe; the acceptor impurities incorporated into the gallium oxide single crystal material recombine with their electron carriers, which can compensate for and reduce the electron concentration in the gallium oxide crystal. This addresses situations with high background impurities, especially when the purity of raw materials and gases is low, resulting in an electron concentration in the melt exceeding 10. 16 / cm 3 The growth conditions should be adjusted to include acceptor impurities.
[0055] In some embodiments of this application, in step (2), the theoretical doping concentration of germanium atoms in the germanium-doped β-Ga2O3 single crystal material is calculated by the following formula:
[0056]
[0057] Where: N d This represents the theoretical doping concentration of germanium atoms, expressed in atoms / cm². 3 ;
[0058] N Ga The density of gallium atoms in a β-Ga₂O₃ single crystal is 3.82 × 10⁻⁶. 22 atoms / cm3;
[0059] f1 represents the abundance of the Ga-69 isotope in gallium oxide, with a value of 0.604.
[0060] f2 represents the abundance of the Ga-71 isotope in gallium oxide, with a value of 0.396.
[0061] ρ1 is the thermal neutron capture cross section of Ga-69, with a value of 1.68 × 10⁻⁶. -24 cm2 ;
[0062] ρ2 represents the thermal neutron capture cross section of Ga-71, with a value of 4.70 × 10⁻⁶. -24 cm 2 ;
[0063] ψ represents the neutron flux of the irradiated neutron source, expressed in n / (cm²). 2 ·s);
[0064] t is the reaction time of neutron irradiation, measured in seconds.
[0065] One of the main innovations of this application is the precise control of the Ge doping concentration by controlling the nuclear reaction process, and the regulation of carrier concentration and conductivity of gallium oxide single crystal materials through Ge doping. The inventors of this application have studied the... 69 Ga、 71 Based on the abundance of Ga isotopes and their reaction cross-section with thermal neutron capture, the parameters for controlling neutron irradiation reaction were determined using commonly used reactor conditions in China. A theoretical formula for calculating the doping concentration of germanium atoms was designed, and the calculation results were verified and the parameters were corrected through neutron irradiation experiments.
[0066] In some embodiments of this application, in step (2), the neutron source for the neutron irradiation treatment includes a reactor neutron source or an accelerator neutron source.
[0067] In some embodiments of this application, the neutron flux of the neutron source is 10. 12 -10 16 n / (cm 2 ·s); for example, 10 12 n / (cm 2 ·s), 10 13 n / (cm 2 ·s), 10 14 n / (cm 2 ·s), 10 15 n / (cm 2 ·s), 10 16 n / (cm 2 ·s) etc.
[0068] This application aims to control the conversion concentration of germanium by regulating the neutron-captured nuclear reaction process. This requires calculating the Ga atom density data in the β-Ga₂O₃ crystal, which is one of the key parameters in the formula for calculating the germanium doping conversion concentration of the β-Ga₂O₃ crystal under neutron irradiation. The calculation process is as follows:
[0069] Given conditions: (1) β-Ga2O3 is a monoclinic crystal system with space group C2 / m; (2) Cell parameters: β=103.7°; each unit cell contains 4 Ga2O3 molecules (i.e. 8 Ga atoms); (3) β-Ga2O3 theoretical density: 5.88 g / cm³ 3 Molar mass: 187.44 g / mol;
[0070] Calculate the unit cell volume V of Ga2O3 based on the given conditions: V=a·b·c·sinβ≈209.7×10 -24 cm 3 ;
[0071] Calculate the atomic density N of Ga. Ga :N Ga = (8 / V)≈3.82×10 22 cm -3 ;
[0072] Verification using the theoretical density of β-Ga₂O₃: N Ga =2×ρ·N a / M≈3.78×10 22 cm -3 ;
[0073] Final result: The Ga atomic density of β-Ga₂O₃ crystal is 3.82 × 10⁻⁶. 22 cm -3 .
[0074] In some embodiments of this application, the neutron irradiation treatment temperature is 78.6°C. During the neutron irradiation treatment, the gallium oxide single crystal material is in a solid state.
[0075] In some embodiments of this application, step (3) includes activation processing including high-temperature activation and / or laser activation. Gallium oxide single crystal materials undergo Ga to Ge conversion after neutron irradiation. Because the irradiation process temperature is below 100°C, Ge at this temperature... 4+ An extra valence electron of an ion remains bound to the atomic nucleus, resulting in a relatively low carrier concentration in gallium oxide single crystal materials. Only by performing activation treatment to allow the valence electron to absorb energy and jump to the conduction band can the concentration of free electrons in gallium oxide single crystal materials be increased, thereby changing the material's conductivity. 4+ After 100% ion activation, the carrier concentration in gallium oxide single crystal material is approximately equal to the germanium doping concentration.
[0076] In some embodiments of this application, the atmosphere for the activation process is an oxygen atmosphere. Because gallium oxide and germanium oxide are highly volatile at high temperatures, introducing an oxygen atmosphere can suppress their volatilization.
[0077] In some embodiments of this application, the high-temperature activation temperature is 700-850℃, such as 700℃, 720℃, 750℃, 780℃, 800℃, 850℃, etc., and the high-temperature activation time is 30-60 minutes, such as 30 minutes, 38 minutes, 43 minutes, 56 minutes, 60 minutes, etc. Because the maximum solubility of germanium in gallium oxide crystal is 5 × 10⁻⁶... 20 / cm 3 After germanium atoms are fully activated, they can release free electrons in a 1:1 ratio. Therefore, the maximum electron concentration of the β-Ga2O3 single crystal material after activation in this application is 5 × 10⁻⁶. 20 / cm 3 .
[0078] This application also provides an n-type high carrier concentration β-Ga2O3 single crystal material, which is prepared by the preparation method of the n-type high carrier concentration β-Ga2O3 single crystal material described in the first aspect of this application.
[0079] In some embodiments of this application, the β-Ga2O3 single crystal material contains germanium as a dopant.
[0080] In some embodiments of this application, the carrier concentration of the β-Ga2O3 single crystal material is 10. 16 -5×10 20 / cm 3 The size of the β-Ga2O3 single crystal material is 50-300mm, such as 50mm, 75mm, 100mm, 150mm, 200mm, 260mm, 300mm, etc.
[0081] The n-type high carrier concentration β-Ga2O3 single crystal material described in this application increases the free carrier concentration of the β-Ga2O3 single crystal material by doping with Ge element. Each germanium atom releases approximately one free electron after activation, thereby changing the conductivity of gallium oxide single crystal.
[0082] In some embodiments of this application, the β-Ga2O3 single crystal material includes one or more of the following: β-Ga2O3 single crystal ingot, β-Ga2O3 single crystal rod, β-Ga2O3 single crystal wafer, and β-Ga2O3 single crystal substrate.
[0083] This application also provides an application of the n-type high carrier concentration β-Ga2O3 single crystal material described in the second aspect of this application in the field of wide bandgap semiconductor devices.
[0084] In some embodiments of this application, the wide bandgap semiconductor device includes a β-Ga2O3 substrate prepared from the n-type high carrier concentration β-Ga2O3 single crystal material, a β-Ga2O3 homoepitaxial wafer, a β-Ga2O3 power device, and a β-Ga2O3 radio frequency device.
[0085] The technical solution of this application will be further described below with reference to specific embodiments.
[0086] Example 1
[0087] A method for preparing an n-type high carrier concentration β-Ga2O3 substrate includes the following steps:
[0088] (1) Preparation of Fe-doped low carrier concentration β-Ga2O3 single crystals and substrates by Czochralski method
[0089] S11. β-Ga2O3 with a diameter of 10 mm, a length of 50 mm, and a
[010] orientation is selected as the seed crystal for growth.
[0090] S12. After thoroughly mixing 1.00 kg of Ga2O3 powder (purity 99.9999%) and 12.32 mg of Fe2O3 powder (purity 99.99%), the mixture is placed into a crucible. The growth furnace is evacuated to a low vacuum until the pressure is less than 10 Pa, and then Ar gas and CO2 gas are introduced. The partial pressure ratio of the two gases is controlled at 85:15. The temperature is raised to 1850℃ to completely melt the Ga2O3 mixed powder. The temperature is maintained for 1 hour to obtain gallium oxide melt.
[0091] S13. Immerse the seed crystal described in step S11 into the melt, controlling the seed crystal rotation speed to 10 rpm. After the seed crystal and melt are fully fused, control the pulling speed to 0.4 mm / h to allow the crystal to grow. Perform necking and shoulder formation sequentially. Once the shoulder diameter reaches the expected size of over 50 mm, adjust the pulling speed to 1.0 mm / h and rotate the shoulder, entering the stable growth stage of the crystal with constant diameter (due to the carrier concentration being controlled at 10). 16 / cm 3 (No spiral growth was observed during this process); after growing to the expected crystal length, the pulling speed was increased to 2.0 mm / h, and the crystal was pulled out to obtain a cylindrical crystal with a regular shape; then it was slowly cooled to room temperature to obtain a β-Ga2O3 single crystal ingot, and its actual carrier concentration was measured to be 1.02*10^6 times in step S15. 14 / cm 3 .
[0092] S14. Cut and roll the above gallium oxide single crystal ingot into a round shape, then cut the cylindrical crystal ingot into a round shape using a multi-wire cutting machine, and then process it into a uniformly thick substrate sheet through grinding, mechanical polishing and chemical polishing. The substrate sheet has a crystal orientation of (001), a diameter of 50 mm and a thickness of about 500 micrometers.
[0093] S15. Characterization and Detection of Samples Before Irradiation
[0094] The crystal phase of the above substrate sample was characterized as β phase using a Bruker D8-Discover X-ray diffractometer. The germanium doping concentration in the above substrate sample was measured using a CAMECA IMS-4F SIMS instrument (germanium impurity detection limit was 2 × 10⁻⁶). 15 cm -3 The carrier concentration of the above substrate samples was measured using a Semilab MCV-530L mercury probe microanalyzer. The characterization and measurement results are shown in Table 1.
[0095] (2) Neutron irradiation and germanium doping
[0096] S21. Set neutron irradiation conditions: Select the reactor neutron source as the neutron irradiation source, and set the neutron flux of the irradiation aperture to 4.77 × 10⁻⁶. 13 / (cm 2 ·s);
[0097] The above-mentioned substrate sample was placed in the irradiation hole for irradiation, and the irradiation treatment time was set to 172,800 s (48 h).
[0098] S22. Calculation of Germanium theoretical doping concentration: The theoretical doping concentration of germanium atoms in the sample is calculated according to the following formula for calculating the germanium conversion concentration of Ga2O3 under neutron irradiation.
[0099]
[0100] Where: N d This represents the theoretical doping concentration of germanium atoms, expressed in atoms / cm². 3 ;
[0101] N Ga The density of gallium atoms in β-Ga₂O₃ is 3.82 × 10⁻⁶. 22 atoms / cm3;
[0102] f1 represents the abundance of the Ga-69 isotope in gallium oxide, with a value of 0.604.
[0103] f2 represents the abundance of the Ga-71 isotope in gallium oxide, with a value of 0.396.
[0104] ρ1 is the thermal neutron capture cross section of Ga-69, with a value of 1.68 × 10⁻⁶. -24 cm 2 ;
[0105] ρ2 represents the thermal neutron capture cross section of Ga-71, with a value of 4.70 × 10⁻⁶. -24 cm2 ;
[0106] ψ represents the neutron flux of the irradiated neutron source, which is 4.77 × 10⁻⁶ in this embodiment. 13 / (cm 2 ·s);
[0107] t is the reaction time of neutron irradiation, measured in seconds.
[0108] The ambient temperature for neutron irradiation treatment was 78.6℃, and the substrate sample was in a solid state during the treatment.
[0109] Substituting the specific parameters of the substrate sample into the above formula, the theoretical concentration of germanium doping is obtained as 9.0 × 10⁻⁶. 17 atoms / cm 3 .
[0110] (3) Germanium atom activation treatment
[0111] The neutron-irradiated substrate sample was placed in a vacuum tube furnace, and oxygen was introduced into the furnace. The furnace was then heated to 800°C at a heating rate of 20°C / min and held at that temperature for 40 min to activate the germanium atoms doped in the sample. Finally, the sample was slowly cooled to room temperature at a cooling rate of 20°C / min. The purpose of using slow heating and cooling methods is to prevent the crystal from cracking due to drastic temperature changes.
[0112] After being activated at high temperature, the free electrons of the germanium-doped substrate sample are activated into conductive charge carriers, resulting in a high-carrier-concentration β-Ga2O3 substrate, denoted as sample A1.
[0113] The crystal phase, germanium doping concentration, and carrier concentration of the A1 sample after neutron irradiation were characterized and measured using a D8-Discover X-ray diffractometer, an IMS-4F SIMS instrument, and a Semilab MCV-530L instrument, respectively. The results are shown in Table 1.
[0114] Example 2
[0115] The preparation method of the high carrier concentration β-Ga2O3 substrate described in Example 2 differs from that in Example 1 only in the neutron irradiation treatment time. In this example, the neutron irradiation treatment time is 345,600 s (96 h), and the resulting high carrier concentration β-Ga2O3 substrate is designated as sample A2.
[0116] The crystal phase, germanium doping concentration, and carrier concentration of the A1 samples before and after neutron irradiation were characterized and measured using a D8-Discover X-ray diffractometer, an IMS-4F SIMS instrument, and a Semilab MCV-530L instrument, respectively. The results are shown in Table 1.
[0117] Example 3
[0118] A method for preparing an n-type high carrier concentration β-Ga2O3 wafer includes the following steps:
[0119] (1) Preparation of unintentionally doped low carrier concentration β-Ga2O3 single crystals and wafers by Czochralski method
[0120] S11. β-Ga2O3 with a diameter of 10 mm, a length of 50 mm, and a
[010] orientation is selected as the seed crystal for growth.
[0121] S12. 1.00 kg of Ga2O3 powder (purity 99.9999%) is filled into a crucible; after the growth furnace is evacuated to a low vacuum until its pressure is less than 10 Pa, Ar gas and CO2 gas are introduced, and the partial pressure ratio of the two gases is controlled at 85:15; the temperature is raised to 1850℃ to completely melt the Ga2O3 mixed powder, and the temperature is kept constant for 1 hour to obtain the melt;
[0122] S13. Immerse the seed crystal described in step S11 into the melt, controlling the seed crystal rotation speed to 10 rpm. After the seed crystal and melt are fully fused, control the pulling speed to 0.4 mm / h to allow the crystal to grow. Perform necking and shoulder formation sequentially. Once the shoulder diameter reaches the expected size of over 50 mm, adjust the pulling speed to 1.0 mm / h and rotate the shoulder, entering the stable growth stage of the crystal with constant diameter (due to the carrier concentration being controlled at 10). 16 / cm 3 (No spiral growth was observed during this period); after growing to the expected crystal length, the pulling speed was increased to 2.0 mm / h, and the crystal was pulled out to obtain a cylindrical crystal with a regular shape; then it was slowly cooled to room temperature to obtain a β-Ga2O3 single crystal ingot, and its actual carrier concentration was measured to be 5.68*10^64 mm / h in step S15. 15 / cm 3 .
[0123] S14. Cut and roll the above gallium oxide single crystal ingot into a round shape, then cut the cylindrical ingot into a round shape using a multi-wire cutter, and then process it into a uniformly thick wafer through grinding, mechanical polishing and chemical polishing. The wafer has a crystal orientation of (001), a diameter of 50 mm and a thickness of about 600 micrometers.
[0124] S15. Characterization and Detection of Samples Before Irradiation
[0125] The crystal phase of the above wafer samples was characterized as β phase using a Bruker D8-Discover X-ray diffractometer. The germanium doping concentration in the above wafer samples was measured using a CAMECA IMS-4F SIMS instrument (germanium impurity detection limit was 2 × 10⁻⁶). 15 cm -3The carrier concentration of the above wafer samples was measured using a Semilab MCV-530L mercury probe microanalyzer. The characterization and measurement results are shown in Table 1.
[0126] (2) Neutron irradiation and germanium doping
[0127] S21. Set neutron irradiation conditions: Select the reactor neutron source as the neutron irradiation source, and set the neutron flux of the irradiation aperture to 4.77 × 10⁻⁶. 13 / (cm 2 ·s);
[0128] The wafer sample was placed in the irradiation hole and irradiated for 172,800 s (48 h).
[0129] S22. Calculation of Germanium theoretical doping concentration: The theoretical doping concentration of germanium atoms in the sample is calculated according to the following formula for calculating the germanium conversion concentration of Ga2O3 under neutron irradiation.
[0130]
[0131] Where: N d This represents the theoretical doping concentration of germanium atoms, expressed in atoms / cm². 3 ;
[0132] N Ga The density of gallium atoms in β-Ga₂O₃ is 3.82 × 10⁻⁶. 22 atoms / cm3;
[0133] f1 represents the abundance of the Ga-69 isotope in gallium oxide, with a value of 0.604.
[0134] f2 represents the abundance of the Ga-71 isotope in gallium oxide, with a value of 0.396.
[0135] ρ1 is the thermal neutron capture cross section of Ga-69, with a value of 1.68 × 10⁻⁶. -24 cm 2 ;
[0136] ρ2 represents the thermal neutron capture cross section of Ga-71, with a value of 4.70 × 10⁻⁶. -24 cm 2 ;
[0137] ψ represents the neutron flux of the irradiated neutron source, which is 4.77 × 10⁻⁶ in this embodiment. 13 / (cm 2 ·s);
[0138] t is the reaction time of neutron irradiation, measured in seconds.
[0139] The ambient temperature for neutron irradiation treatment was 78.6℃, and the wafer sample was in a solid state during the treatment.
[0140] Substituting the specific parameters of the wafer sample into the above formula, the theoretical doping concentration of germanium after neutron irradiation is obtained as 9.0 × 10⁻⁶. 17 atoms / cm 3 .
[0141] (3) Germanium atom activation treatment
[0142] The neutron-irradiated wafer was placed in a vacuum tube furnace, and oxygen was introduced into the furnace. The furnace was then heated to 800°C at a heating rate of 20°C / min and held at that temperature for 40 minutes to activate the germanium atoms doped in the sample. Finally, the wafer was slowly cooled to room temperature at a cooling rate of 20°C / min. The purpose of using slow heating and cooling methods is to prevent the crystal from cracking due to drastic temperature changes.
[0143] After being activated at high temperature, the free electrons of the germanium-doped wafer are activated into conductive charge carriers, resulting in a high-carrier-concentration β-Ga2O3 wafer, denoted as sample A3.
[0144] The crystal phase, germanium doping concentration, and carrier concentration of the A3 sample after neutron irradiation were characterized and measured using a D8-Discover X-ray diffractometer, an IMS-4F SIMS instrument, and a Semilab MCV-530L instrument, respectively. The results are shown in Table 1.
[0145] Example 4
[0146] The preparation method of the n-type high carrier concentration β-Ga2O3 wafer described in Example 4 differs from that in Example 3 only in the neutron irradiation treatment time. In this example, the neutron irradiation treatment time is 345,600 s (96 h), and the resulting high carrier concentration β-Ga2O3 wafer is designated as sample A4.
[0147] The crystal phase, germanium doping concentration, and carrier concentration of the A4 sample before and after neutron irradiation were characterized and measured using a D8-Discover X-ray diffractometer, an IMS-4F SIMS instrument, and a Semilab MCV-530L instrument, respectively. The results are shown in Table 1.
[0148] Example 5
[0149] The preparation method of the n-type high carrier concentration β-Ga2O3 wafer described in Example 5 differs from that in Example 3 only in that the temperature of germanium atom activation treatment is 600℃ and the activation time is 40min; the n-type high carrier concentration β-Ga2O3 wafer prepared in Example 5 is designated as sample A5.
[0150] The germanium atom concentration and carrier concentration of the A5 sample after germanium activation treatment were measured using an IMS-4F SIMS instrument and a Semilab MCV-530L instrument, respectively. The results were plotted... Figure 1 .
[0151] Example 6
[0152] The difference between the preparation method of the n-type high carrier concentration β-Ga2O3 wafer in Example 6 and that in Example 3 is that the temperature of the germanium atom activation treatment is 700℃ and the activation time is 40min; the n-type high carrier concentration β-Ga2O3 wafer prepared in Example 6 is denoted as sample A6.
[0153] The germanium atom concentration and carrier concentration of the A6 sample after germanium activation treatment were measured using an IMS-4F SIMS instrument and a Semilab MCV-530L instrument, respectively. The results were plotted... Figure 1 .
[0154] Example 7
[0155] The difference between the preparation method of the n-type high carrier concentration β-Ga2O3 wafer in Example 7 and that in Example 3 is that the temperature of germanium atom activation treatment is 900℃ and the activation time is 40min; the n-type high carrier concentration β-Ga2O3 wafer prepared in Example 7 is denoted as sample A7.
[0156] The germanium atom concentration and carrier concentration of the A7 sample after germanium activation treatment were measured using an IMS-4F SIMS instrument and a Semilab MCV-530L instrument, respectively. The results were plotted... Figure 1 .
[0157] Comparative Example 1
[0158] The preparation method of the n-type high carrier concentration β-Ga2O3 wafer described in Comparative Example 1 differs from that in Example 3 only in that germanium atom activation treatment is not performed. The aim is to compare and analyze the effect of the activation treatment process on the carrier concentration. An unactivated n-type β-Ga2O3 wafer was prepared and designated as Sample B1.
[0159] The crystal phase, germanium doping concentration, and carrier concentration of the B1 sample after neutron irradiation were characterized and measured using a D8-Discover X-ray diffractometer, an IMS-4F SIMS instrument, and a Semilab MCV-530L instrument, respectively. The results are shown in Table 1.
[0160] Comparative Example 2
[0161] The preparation method of the n-type high carrier concentration β-Ga2O3 wafer described in Comparative Example 2 differs from that in Example 4 only in that germanium atom activation treatment is not performed. The aim is to compare and analyze the effect of the activation treatment process on the carrier concentration. An unactivated n-type β-Ga2O3 wafer was prepared and designated as sample B2.
[0162] The crystal phase, germanium doping concentration, and carrier concentration of the B2 sample after neutron irradiation were characterized and measured using a D8-Discover X-ray diffractometer, an IMS-4F SIMS instrument, and a Semilab MCV-530L instrument, respectively. The results are shown in Table 1.
[0163] Table 1
[0164]
[0165] As can be seen from Table 1: (1) Samples A1 and A2 were doped with Fe impurities during the preparation process by the Czochralski method. Before neutron irradiation, their carrier concentrations were lower than those of the unintentionally doped samples A3 and A4 (4.15-5.68*10). 15 / cm 3 ), and below 10 16 / cm 3 This indicates that the Fe impurity doping reduces the background carrier concentration; after neutron irradiation treatment, the carrier concentration of samples A1 and A2 increased by 3-4 orders of magnitude, which can meet the requirements for use on conductive gallium oxide substrates. This shows that the combination of Czochralski and neutron irradiation processes designed in this application can prepare gallium oxide single crystal materials with high carrier concentration.
[0166] (2) Actual measured concentration of germanium in samples A1 and A3 (1.1 × 10⁻⁶) 18 toms / cm 3 ) and the theoretical germanium doping concentration calculated by the formula (9.0 × 10⁻⁶) 17 atoms / cm 3 The actual measured concentrations of germanium in samples A2 and A4 are very close; the actual measured concentrations are 2.0–2.2 × 10⁻⁶. 18 toms / cm 3 ) and the theoretical germanium doping concentration calculated by the formula (1.8 × 10⁻⁶) 18 atoms / cm 3 The results are comparable, therefore, the experimental data verifies that the inventor's theoretical doping concentration calculation formula for gallium germanium oxide is feasible and can be used to design neutron irradiation processes and precisely control the doping concentration of gallium germanium oxide. It should be noted that the germanium atom concentration measured by the secondary ion mass spectrometer used in the above embodiments has a relatively large error, which further highlights the value of the theoretical germanium doping concentration calculation formula in gallium oxide.
[0167] (3) Before neutron irradiation, samples A1, A2, A3 and A4 all had the β phase. After neutron irradiation and activation treatment, the crystal phase of each sample did not change. The results show that neutron irradiation under certain conditions will not change the crystal phase of gallium oxide single crystal material.
[0168] The effect of different activation temperatures on germanium doping concentration and carrier concentration in β-Ga2O3 wafers.
[0169] Based on the carrier concentration variation patterns in Examples 3, 5-7, and Comparative Example 1, a graph showing the relationship between different activation temperatures and germanium doping concentration and carrier concentration was plotted, as follows: Figure 1 As shown in the figure. The activation temperature corresponding to Example 3 is 800℃.
[0170] from Figure 1 It can be seen that the germanium atom doping concentration at different activation temperatures is basically a parallel straight line, indicating that the germanium atom doping concentration is a constant and has no relation to the activation temperature. Combined with the carrier concentration of Comparative Example 1 (unactivated), the carrier concentration increased by nearly one order of magnitude after activation at 600℃ (Example 5). As the activation temperature increases, the carrier concentration increases accordingly, indicating that the activation rate of germanium ions increases. When the activation temperature is 800℃ (Example 3), the carrier concentration reaches its peak, which is comparable to the germanium doping concentration, indicating that most of the free electrons are activated. When the activation temperature is further increased, the carrier concentration tends to saturate and no longer increases.
[0171] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.
Claims
1. A method for preparing an n-type high carrier concentration β-Ga2O3 single crystal material, characterized in that, Includes the following steps: (1) β-Ga2O3 single crystal material with low carrier concentration was prepared by melt method; (2) Calculate the theoretical doping concentration of germanium atoms in β-Ga2O3 single crystal material; neutron irradiation treatment is performed on β-Ga2O3 single crystal material with low carrier concentration to obtain germanium-doped β-Ga2O3 single crystal material. (3) The germanium-doped β-Ga2O3 single crystal material is activated to obtain the n-type high carrier concentration β-Ga2O3 single crystal material.
2. The method for preparing n-type high carrier concentration β-Ga2O3 single crystal material according to claim 1, characterized in that, In step (1), the carrier concentration of the low carrier concentration β-Ga2O3 single crystal material is ≤10. 16 / cm 3 ; And / or, the preparation method of the β-Ga2O3 single crystal material with low carrier concentration includes one or more of the following: Czochralski method, mode-guided method and Bridgman method; preferably, the Czochralski method; And / or, the controlled method for preparing β-Ga2O3 single crystal materials with low carrier concentration by the melt method includes unintentional doping or doping with acceptor impurities; more preferably, the acceptor impurities include one or more of Fe, N and Mg.
3. The method for preparing n-type high carrier concentration β-Ga2O3 single crystal material according to claim 1, characterized in that, In step (2), the theoretical doping concentration of germanium atoms in the germanium-doped β-Ga2O3 single crystal material is calculated using the following formula: Where: N d This represents the theoretical doping concentration of germanium atoms, expressed in atoms / cm². 3 ; N Ga The density of gallium atoms in a β-Ga₂O₃ single crystal is 3.82 × 10⁻⁶. 22 atoms / cm 3 ; f1 represents the abundance of the Ga-69 isotope in gallium oxide, with a value of 0.
604. f2 represents the abundance of the Ga-71 isotope in gallium oxide, with a value of 0.
396. ρ1 is the thermal neutron capture cross section of Ga-69, with a value of 1.68 × 10⁻⁶. -24 cm 2 ; ρ2 is the thermal neutron capture cross section of Ga-71, with a value of 4.70 × 10⁻⁶. -24 cm 2 ; ψ represents the neutron flux of the irradiated neutron source, expressed in n / (cm²). 2 ·s); t is the reaction time of neutron irradiation, measured in seconds.
4. The method for preparing n-type high carrier concentration β-Ga2O3 single crystal material according to claim 1, characterized in that, In step (2), the neutron source for the neutron irradiation treatment includes a reactor neutron source or an accelerator neutron source.
5. The method for preparing n-type high carrier concentration β-Ga2O3 single crystal material according to claim 4, characterized in that, The neutron flux of the neutron source is 10. 12 -10 16 n / (cm 2 ·s).
6. The method for preparing n-type high carrier concentration β-Ga2O3 single crystal material according to claim 1, characterized in that, In step (3), the activation process includes high-temperature activation and / or laser activation; And / or, the atmosphere for the activation process is an oxygen atmosphere.
7. The method for preparing n-type high carrier concentration β-Ga2O3 single crystal material according to claim 6, characterized in that, The high-temperature activation temperature is 700-850℃, and the high-temperature activation time is 30-60 minutes.
8. A type n-type high carrier concentration β-Ga₂O₃ single crystal material, characterized in that, Prepared by the preparation method according to any one of claims 1-7; Preferably, the β-Ga2O3 single crystal material contains germanium as a dopant. Preferably, the carrier concentration of the β-Ga2O3 single crystal material is 10. 16 -5×10 20 / cm 3 The size of the β-Ga2O3 single crystal material is 50-300 mm.
9. The n-type high carrier concentration β-Ga₂O₃ single crystal material according to claim 8, characterized in that, The β-Ga2O3 single crystal material includes one or more of the following: β-Ga2O3 single crystal ingot, β-Ga2O3 single crystal rod, β-Ga2O3 single crystal wafer, and β-Ga2O3 single crystal substrate.
10. The application of the n-type high carrier concentration β-Ga2O3 single crystal material according to any one of claims 8-9 in the field of wide bandgap semiconductor devices.