Preparation method of gallium oxide semi-insulating substrate and gallium oxide semi-insulating substrate

Abstract

The invention discloses a preparation method of a gallium oxide semi-insulating substrate and the gallium oxide semi-insulating substrate, which comprises the following steps: performing proton irradiation treatment on a gallium oxide single-crystal substrate to introduce lattice defects into the gallium oxide single-crystal substrate, and performing annealing treatment on the gallium oxide single-crystal substrate into which the lattice defects are introduced to obtain the gallium oxide semi-insulating substrate. According to the technical scheme, lattice defects are introduced into the gallium oxide single crystal substrate by adopting a proton irradiation process to form a deep energy level trap to effectively capture free carriers, so that the carrier concentration of the material is remarkably reduced, and the resistivity of the material is increased, thereby realizing stable conversion from a conductive state to a semi-insulating state; therefore, the conditions of poor doping uniformity, insufficient thermal stability and local resistivity fluctuation existing in a traditional element doping method are overcome, meanwhile, the defects of lattice mismatch, insufficient thermal conductivity and the like caused by a heterogeneous substrate are avoided, and the electrical property uniformity and the material structure integrity of the gallium oxide substrate are effectively improved. The method has the advantages of non-contact, low cost, easy regulation and control and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a preparation method of a gallium oxide semi-insulating substrate and a gallium oxide semi-insulating substrate. BACKGROUND

[0002] Gallium oxide (Ga2O3) is a new emerging ultra-wide bandgap semiconductor material, which has a wide application prospect in the fields of power electronic devices and deep ultraviolet photodetectors due to its excellent breakdown field strength, high thermal stability and wide bandgap characteristics. However, the application of gallium oxide in actual device preparation still faces key technical bottlenecks, especially in the preparation of high-quality semi-insulating substrates, which still lacks mature and reliable solutions.

[0003] At present, the mainstream technology for preparing gallium oxide semi-insulating substrates mainly includes element doping method and hetero-substrate method. Among them, the element doping method usually adopts acceptor impurities such as iron (Fe), magnesium (Mg) and zinc (Zn) to compensate for intrinsic donor defects and improve the resistivity of the material. However, such methods have problems such as poor impurity doping uniformity, poor thermal stability, large carrier concentration fluctuation, etc., which seriously affect the stability and consistency of device performance. The hetero-substrate method uses SiC, sapphire and other materials as epitaxial substrates, but due to the existence of lattice mismatch and thermal expansion coefficient difference, it is easy to cause excessive stress of the epitaxial layer, high defect density and insufficient thermal conductivity, which affects the reliability and service life of the device, especially in high-frequency high-power device applications.

[0004] In addition, there are a large number of intrinsic donor defects in gallium oxide materials, such as oxygen vacancies (V_O) and gallium interstitial atoms (Ga_i), which are easy to ionize to form free electrons at room temperature, making the material exhibit intrinsic conductivity characteristics, which is difficult to meet the demand of high resistivity semi-insulating substrate for devices. Therefore, the high concentration compensation doping or traditional defect engineering means relied on by the prior art produces significant parasitic effects and leakage current, which seriously affects the working efficiency and reliability of the device, and there are still obvious limitations in regulating the carrier concentration of the material.

[0005] Therefore, the related technology needs to be improved. SUMMARY

[0006] The main purpose of the present application is to provide a preparation method of a gallium oxide semi-insulating substrate and related devices, which aims to at least solve the technical problems of poor impurity doping uniformity, poor thermal stability, large carrier concentration fluctuation and the like mentioned in the background art.

[0007] In a first aspect, the present application provides a preparation method of a gallium oxide semi-insulating substrate, which comprises the following steps: proton irradiation treatment is performed on a gallium oxide single crystal substrate with a predetermined thickness to introduce lattice defects in the gallium oxide single crystal substrate; The gallium oxide single crystal substrate, into which the lattice defects have been introduced, is subjected to annealing treatment; A gallium oxide semi-insulating substrate is obtained; wherein, the gallium oxide semi-insulating substrate refers to a gallium oxide substrate in a semi-insulating state.

[0008] Based on the first aspect, the lattice defects include oxygen vacancy defects, gallium vacancy defects, and oxygen antisite defects.

[0009] Based on the first aspect, the oxygen vacancy defects, gallium vacancy defects, and oxygen antisite defects are formed in the bandgap of the gallium oxide single crystal substrate and act as deep-level traps for capturing free charge carriers.

[0010] Based on the first aspect, the injection energy of the proton irradiation treatment is 40-80 MeV.

[0011] Based on the first aspect, the dose of the proton irradiation treatment is 1×10¹ 6 Up to 1×10¹ 8 Ions per square centimeter.

[0012] Based on the first aspect, the annealing treatment temperature range is 400°C to 800°C, and the annealing time is 0.5 hours to 2 hours.

[0013] Based on the first aspect, the preset thickness of the gallium oxide single crystal substrate is 200 to 1000 micrometers.

[0014] Based on the first aspect, the gallium oxide single crystal substrate is unintentionally doped gallium oxide.

[0015] Based on the first aspect, the step of obtaining the gallium oxide semi-insulating substrate specifically includes: Multiple unit samples are cut from the gallium oxide semi-insulating substrate along the thickness direction.

[0016] In a second aspect, the present invention provides a gallium oxide semi-insulating substrate, which is fabricated using the gallium oxide semi-insulating substrate preparation method described in the first aspect.

[0017] The present invention discloses a method for preparing a gallium oxide semi-insulating substrate and the gallium oxide semi-insulating substrate itself. This method employs a proton irradiation process to introduce lattice defects into a gallium oxide single-crystal substrate, forming deep-level traps to effectively capture free charge carriers. This significantly reduces the charge carrier concentration and increases the resistivity of the material, thereby achieving a stable transition from a conductive state to a semi-insulating state. This overcomes the problems of poor doping uniformity, insufficient thermal stability, and local resistivity fluctuations inherent in traditional elemental doping methods. Simultaneously, it avoids defects such as lattice mismatch and insufficient thermal conductivity caused by heterogeneous substrates. This effectively improves the electrical performance uniformity, material structural integrity, and compatibility with subsequent devices of the gallium oxide substrate, and possesses advantages such as non-contact operation, low cost, and easy control. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of a method for preparing a gallium oxide semi-insulating substrate according to an embodiment of this application; Figure 2 This is a schematic diagram illustrating the irradiation treatment of the gallium oxide single crystal substrate using a high-energy proton beam in an embodiment of this application; Figure 3 This is a schematic diagram illustrating the introduction of lattice defects through proton irradiation treatment in step S101 in an embodiment of this application. Figure 4 This is a schematic flowchart illustrating a method for preparing a gallium oxide semi-insulating substrate according to an embodiment of this application.

[0020] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0022] It should be noted that related terms such as "first" and "second" can be used to describe various components, but these terms do not limit the component. These terms are only used to distinguish one component from another. For example, without departing from the scope of the invention, the first component can be referred to as the second component, and the second component can similarly be referred to as the first component. The term "and / or" refers to any one or more combinations of related and descriptive terms.

[0023] Gallium oxide (Ga2O3), as a new generation of wide-bandgap semiconductor material, has shown great potential in power electronics and deep-ultraviolet optoelectronic devices. However, its practical application faces a key bottleneck: how to obtain high-quality semi-insulating substrates. Current mainstream semi-insulating methods all have significant shortcomings. While doping with elements such as Fe can improve resistivity, the problems of doping inhomogeneity and poor thermal stability severely restrict the consistency of device performance. Using heterogeneous substrates such as SiC or sapphire faces challenges of insufficient thermal conductivity and lattice mismatch, making it difficult to guarantee the quality of the epitaxial layer. Especially in high-frequency applications, substrates prepared by these traditional methods often exhibit significant parasitic effects and leakage currents, severely impacting device efficiency and reliability. Therefore, developing novel gallium oxide semi-insulating substrate preparation technologies to achieve more uniform resistivity distribution, better thermal stability, and lower defect density has become a key breakthrough for promoting the practical application of Ga2O3 devices. This not only relates to improving the performance of the basic material but will also directly affect technological advancements in key areas such as 5G communication and smart grids. To address these issues, a method for realizing gallium oxide semi-insulating substrates using proton irradiation is proposed. A key feature is that high-energy proton irradiation introduces defects into the gallium oxide crystal. These defects act as carrier traps, capturing free electrons or holes, thereby reducing the carrier concentration and increasing the resistivity of the material. This causes gallium oxide to gradually transition from its original conductive state to a semi-insulating state.

[0024] Among related technologies, proton irradiation technology has significant advantages in the fabrication of semi-insulating gallium oxide substrates. By flexibly adjusting key parameters such as irradiation energy, dose, and time, proton irradiation can precisely introduce defects into gallium oxide materials, thereby causing specific changes in the material's electrical properties and achieving an ideal semi-insulating state. This precise control capability gives proton irradiation technology a unique advantage in the fabrication of high-performance semiconductor devices. Secondly, proton irradiation is a non-contact operation, applying no mechanical force to the material surface throughout the process, effectively avoiding mechanical damage that may occur with contact processing. This not only helps maintain the integrity of the material's crystal structure but also ensures that its surface flatness is not affected. This is crucial for subsequent device fabrication and applications, as surface flatness and crystal structure integrity directly affect device performance and reliability. Finally, proton irradiation technology is characterized by low cost and high efficiency. Compared to traditional fabrication processes, the equipment used in proton irradiation is simpler in construction, with relatively lower purchase and maintenance costs. Moreover, the proton irradiation process is short, efficiently completing material processing in a short time, significantly improving production efficiency. This is of great significance for large-scale production and industrial application, as it can effectively reduce production costs and enhance market competitiveness.

[0025] However, the related technologies have the following problems when preparing gallium oxide (Ga2O3) semi-insulating substrates: (1) Gallium oxide (especially β-Ga2O3) contains a large number of intrinsic donor defects (such as oxygen vacancies V). O Ga interstitial atoms i These defects are prone to ionization, generating free electrons, which makes it difficult to reduce intrinsic conductivity. They need to be suppressed by high-concentration compensating doping or defect engineering, but the effect is not good.

[0026] (2) Related methods rely on doping with acceptor impurities (such as Mg, Zn, etc.) to compensate for intrinsic donors. However, the acceptor energy level is deep, the ionization efficiency is low at room temperature, and the doping uniformity is difficult to control, which easily leads to local carrier concentration fluctuations and uneven resistivity distribution.

[0027] To resolve the above technical issues, please refer to Figure 1 This application provides a method for preparing a gallium oxide semi-insulating substrate to prepare a functional substrate material suitable for use as a power device and a radio frequency device.

[0028] The preparation method includes at least the following steps: Step S101: Proton irradiation treatment is performed on a gallium oxide single crystal substrate of a preset thickness to introduce lattice defects into the gallium oxide single crystal substrate.

[0029] In this embodiment, a gallium oxide single crystal substrate of a predetermined thickness is first provided (as the initial material). This gallium oxide single crystal substrate is unintentionally doped, preferably β-Ga₂O₃, to ensure its crystal integrity and processing adaptability. Subsequently, the gallium oxide single crystal substrate is irradiated using a high-energy proton beam (see [reference]). Figure 2 The process of proton injection introduces lattice defects into the substrate crystal structure. These lattice defects form deep-level traps in the band gap of the material, which can effectively capture free electrons or holes, thereby reducing the carrier concentration and providing a physical basis for the subsequent realization of a semi-insulating state.

[0030] The proton source can be the China Advanced Research Reactor (CARR), also known as the "Yanlong" pool reactor, built by the China Institute of Atomic Energy. The high-energy proton beam generated by this facility can be used to precisely irradiate the surface of the gallium oxide single crystal substrate in a vertical irradiation manner.

[0031] It should be noted that during proton irradiation, the irradiation energy and dose can be set according to the actual device performance requirements, exhibiting good parameter control capability and spatial uniformity, which is beneficial for the consistent control of defect concentration throughout the entire wafer. Through this step (proton irradiation treatment), a defect state structure (lattice defect) with stable electrical control capability is formed inside the gallium oxide crystal, laying the foundation for subsequent annealing heat treatment and final semi-insulating properties.

[0032] Furthermore, the gallium oxide single-crystal substrate is unintentionally doped gallium oxide, meaning that no exogenous impurity elements were intentionally introduced during crystal growth. This type of substrate has a low initial carrier concentration and good crystal integrity, which is beneficial for achieving efficient defect control and resistivity improvement through subsequent proton irradiation without interference from external elements. Compared to acceptor-doped gallium oxide substrates, unintentionally doped materials avoid problems such as doping inhomogeneity and thermal instability, helping to improve the consistency of irradiation treatment and the spatial uniformity of the semi-insulating state. Therefore, choosing unintentionally doped gallium oxide as the initial material is a key foundation for realizing high-performance gallium oxide semi-insulating substrates.

[0033] Step S102: Anneal the gallium oxide single crystal substrate that has been introduced with lattice defects.

[0034] In this embodiment, the gallium oxide single crystal substrate, which has been subjected to proton irradiation and has lattice defects, is annealed to optimize the crystal structure, stabilize beneficial defect states, and further improve the electrical properties of the material. This annealing process is carried out in an inert atmosphere (such as nitrogen or argon) or a vacuum environment to avoid secondary interference to the crystal structure caused by redox reactions.

[0035] It should be noted that this annealing treatment can effectively eliminate some of the non-targeted lattice damage introduced by the irradiation process, repair local structural distortions in the crystal, and promote the stable formation of carrier trap energy levels, making the defect-induced resistivity enhancement effect more persistent and controllable.

[0036] In short, this annealing process can maintain the crystal integrity of the gallium oxide single crystal substrate while making the defect structure (lattice defect) formed in its lattice more stable. This results in a further reduction in the overall carrier concentration and a further increase in resistivity, laying the foundation for the subsequent realization of a semi-insulating substrate.

[0037] Step S103 yields a gallium oxide semi-insulating substrate.

[0038] In this embodiment, the gallium oxide single-crystal substrate, after proton irradiation and annealing, forms stable lattice defects in its crystal structure, especially deep-level defect states such as oxygen vacancies, gallium vacancies, and antisite defects. These defects introduce trap levels in the gallium oxide bandgap, which can effectively capture free carriers, significantly reduce the electron concentration of the material, and greatly increase its resistivity. Ultimately, this transforms the gallium oxide material from its original conductive state to a semi-insulating state (i.e., the resulting gallium oxide semi-insulating substrate is a gallium oxide substrate in a semi-insulating state).

[0039] It should be understood that the carrier concentration of a gallium oxide single-crystal substrate in the conductive state ranges from approximately 1 × 10¹. 7 Up to 1×10¹8 cm -3 The corresponding resistivity is typically between 10² and 10⁻⁶. 4 Between Ω·cm, gallium oxide exhibits obvious n-type conductivity, making it unsuitable as an insulating substrate for high-frequency power devices. In contrast, the semi-insulating gallium oxide substrate in its semi-insulating state forms a large number of deep-level defect states, significantly suppressing the presence of free carriers, reducing the carrier concentration to approximately 1×10¹³ to 1×10¹³. 4 cm -3 The corresponding resistivity increases significantly to 10. 6 Up to 10 8 Materials in this state with a resistivity of Ω·cm are defined as "gallium oxide semi-insulating substrates". They have high resistivity and low leakage current characteristics, making them suitable as functional substrate materials for power devices and radio frequency devices.

[0040] Thus, through the above processing steps, compared to the original untreated gallium oxide single crystal substrate, a gallium oxide semi-insulating substrate with high resistivity and low carrier concentration is obtained through steps S101 to S103. This gallium oxide semi-insulating substrate exhibits good electrical uniformity, thermal stability, and material integrity, making it suitable for subsequent epitaxial device growth and high-frequency, high-voltage applications. It is particularly suitable as a base substrate material for power devices, radio frequency devices, and deep ultraviolet optoelectronic devices. The "gallium oxide semi-insulating substrate" mentioned in this step specifically refers to a gallium oxide crystal substrate in a semi-insulating state. Its key physical characteristics are a controlled decrease in carrier concentration and a significant increase in resistivity, exhibiting near-insulating behavior while still retaining certain semiconductor properties.

[0041] As can be seen, the gallium oxide semi-insulating substrate preparation method and gallium oxide semi-insulating substrate of this application use a proton irradiation process to introduce lattice defects in the gallium oxide single crystal substrate, forming deep energy level traps to effectively capture free charge carriers, significantly reducing the charge carrier concentration of the material, thereby achieving a stable transition from a conductive state to a semi-insulating state. This overcomes the problems of poor doping uniformity, insufficient thermal stability and local resistivity fluctuations in traditional element doping methods, while avoiding defects such as lattice mismatch and insufficient thermal conductivity caused by heterogeneous substrates. It effectively improves the electrical performance uniformity, material structure integrity and compatibility of gallium oxide substrates, and has the advantages of non-contact, low cost and easy control.

[0042] In some optional embodiments of this application, lattice defects include oxygen vacancy defects, gallium vacancy defects, and oxygen antisite defects.

[0043] For details, please refer to Figure 3The lattice defects introduced by the proton irradiation treatment in step S101 include, but are not limited to, oxygen vacancy defects (V_O), gallium vacancy defects (V_Ga), and oxygen antisite defects (O_Ga). These point defects can form deep-level traps in the band gap of gallium oxide materials to capture the original free carriers in the material, especially electrons, thereby effectively reducing the overall carrier concentration, increasing the resistivity of the material, and realizing the stable transition of gallium oxide from a conductive state to a semi-insulating state.

[0044] The following provides some explanation of oxygen vacancy defects (V_O), gallium vacancy defects (V_Ga), and oxygen antisite defects (O_Ga): Oxygen vacancy defects (V_O) indicate local regions in a material where oxygen atoms are missing. Under certain dosage and annealing conditions, the presence of V_O indicates that irradiation produces a defect modulation effect and also shows that the lattice mismatch caused by irradiation enters the effective deep energy level induction range.

[0045] Gallium vacancy defects (V_Ga) indicate the vacancy status of Ga sites in a crystal and are an important signal for determining whether a material has effective "acceptor trap" behavior. Their appearance indicates that an electron concentration suppression mechanism has been established.

[0046] Oxygen antisite defects (O_Ga) indicate the occurrence of antisite mismatches (structural distortions) in crystals, suggesting that proton energy and dose are sufficient to trigger crystal rearrangement and influence more complex lattice transformations. The presence of oxygen antisite defects indicates that the energy and dose of proton irradiation have reached the threshold condition for inducing complex structural transformations in the lattice, possessing sufficient capability to break the original lattice order and reconstruct novel locally stable structures. Furthermore, this defect can induce significant bandgap perturbations and local electric field changes in the gallium oxide bandgap, forming deep-level traps that efficiently capture free electrons.

[0047] It should be understood that during the process of introducing lattice defects through proton irradiation, the resulting oxygen vacancy defects, gallium vacancy defects, and oxygen antisite defects are mainly distributed in the bandgap region of the gallium oxide single-crystal substrate. These defect states manifest as deep-level traps in the energy band, effectively capturing free charge carriers, especially electrons, in the material, thereby significantly reducing the charge carrier concentration and enhancing the resistivity properties of the material. This deep-level trap mechanism constitutes the key physical basis for the transformation of gallium oxide from a conductive state to a semi-insulating state.

[0048] In some optional embodiments of this application, the proton irradiation treatment uses an injection energy ranging from 40 to 80 MeV, the specific value of which can be selected and optimized based on the thickness of the gallium oxide substrate and the expected defect introduction depth. Higher injection energies facilitate deeper defect distribution within the material, while lower energies are suitable for thinner substrates or shallower layer manipulation. By adjusting the proton injection energy, fine control over the depth of defect distribution within the crystal can be achieved, thereby improving carrier trapping efficiency and enhancing the spatial consistency and stability of the semi-insulating properties.

[0049] In one embodiment, when the proton injection energy is set to 50 MeV, effective penetration distribution of defects can be achieved in a 650-micrometer-thick gallium oxide substrate, while taking into account both the preservation of the crystal structure and the defect-induced electrical modulation effect, providing a better parameter selection for achieving highly consistent and stable semi-insulating properties.

[0050] In addition, in proton irradiation treatment, the proton injection dose can be set to 1×10¹. 6 Up to 1×10¹ 8 Ions per square centimeter (ions / cm²) are used to regulate the concentration and distribution density of defects in the crystal lattice, thereby effectively reducing the carrier concentration of gallium oxide materials.

[0051] In one embodiment, the proton injection dose is set to 1 × 10¹ 7 At ions / cm², combined with an injection energy of 50 MeV, a moderately saturated distribution of defects can be achieved in a 650-micrometer-thick gallium oxide substrate. This not only forms a continuous and effective deep-level trap structure but also avoids irreversible damage to the crystal structure caused by excessive irradiation, exhibiting the best semi-insulating process effect and wafer-level uniformity.

[0052] In some optional embodiments of this application, the annealing treatment following proton irradiation is performed at a temperature ranging from 400°C to 800°C for a duration of 0.5 hours to 2 hours. This heat treatment process helps repair non-targeted lattice damage generated during irradiation, stabilizes deep-level defect states, and improves the overall crystal quality and electrical uniformity of the material. The selection of temperature and time can be flexibly adjusted according to proton injection conditions, target resistivity range, and substrate thickness to obtain optimal carrier trap activation effect and structural stability.

[0053] In one embodiment, the annealing temperature is set to 600°C, the annealing time is controlled to be 1 hour, and the heat treatment is carried out in an inert atmosphere (such as nitrogen or argon). This combination of parameters can fully activate the deep-level trap structure introduced by proton irradiation without destroying the gallium oxide crystal structure, while eliminating some of the irradiation-induced lattice distortion, thus improving the thermal stability and resistivity consistency of the material. Experiments have shown that this annealing condition, combined with a 50 MeV injection energy and a 1×10¹⁰ annealing temperature, is effective. 7 The combined use of ions / cm² dosage can synergistically achieve a stable transition of gallium oxide from a conductive state to a semi-insulating state, which is the preferred process route for obtaining high-performance semi-insulating substrates.

[0054] In some optional embodiments of this application, the preset thickness of the gallium oxide single-crystal substrate ranges from 200 to 1000 micrometers (μm). This thickness setting satisfies the penetration depth requirement for the proton beam to form an effective defect distribution within the material, while also facilitating subsequent device fabrication and structural stability control. An excessively thin substrate may result in insufficient penetration into defect areas, affecting the semi-insulating effect; an excessively thick substrate may introduce internal stress and reduce process uniformity. By rationally setting the thickness parameters, both material processability and application adaptability can be considered while ensuring semi-insulating performance.

[0055] In one embodiment, when the thickness of the gallium oxide single-crystal substrate is set to 650 micrometers, this thickness matches the proton injection energy of 50 MeV, ensuring sufficient penetration depth and defect introduction range of the proton beam within the substrate crystal, thereby forming a uniform and effective deep-level trap distribution throughout the thickness direction. Simultaneously, this thickness exhibits good structural stability and compatibility with subsequent processing, making it a preferred thickness parameter for achieving high-quality semi-insulating gallium oxide substrates.

[0056] Please see Figure 4 The steps for obtaining the gallium oxide semi-insulating substrate specifically include: Step S404: Cut multiple unit samples along the thickness direction of the gallium oxide semi-insulating substrate.

[0057] In this embodiment, the gallium oxide semi-insulating substrate is cut along its thickness direction to obtain multiple unit samples with the same semi-insulating properties. Preferably, high-precision methods such as laser cutting, mechanical scribing, or plasma dry etching are used to divide the wafer into several thin slices with a thickness of approximately 100 micrometers. The above cutting operations should be performed while maintaining the integrity of the crystal structure and the surface flatness to avoid introducing new mechanical stress or surface damage.

[0058] The individual unit samples obtained from the cutting process can be used as test samples for electrical performance characterization (such as Hall effect testing and resistivity testing), or as functional substrates for subsequent epitaxial growth and device fabrication. This step further improves the material's processability, utilization rate, and functional scalability, meeting the specific needs of different application scenarios.

[0059] This application also provides a gallium oxide semi-insulating substrate, which is fabricated using the gallium oxide semi-insulating substrate preparation method described in the above embodiments.

[0060] First, an unintentionally doped gallium oxide (Ga2O3) single-crystal substrate is provided, preferably β-Ga2O3, with a thickness set between 200 and 1000 micrometers, more preferably 650 micrometers, to ensure matching the penetration depth of the high-energy proton beam. Subsequently, the substrate is subjected to vertical proton implantation using a high-flux proton source device (such as the China Advanced Research Reactor (CARR)). The proton implantation energy is controlled between 40 and 80 MeV, and the dose is set at 1 × 10¹. 6 Up to 1×10¹ 8 The parameters are set to ions / cm² to enable tunable intervention in the lattice depth and defect density. This combination of parameters can create a slightly shallower but denser defect distribution layer within the crystal, making it suitable for constructing deep-level traps on thin substrates.

[0061] During this process, when the high-energy proton beam penetrates the gallium oxide crystal, it undergoes inelastic collisions with lattice atoms, triggering the breaking of Ga-O bonds, atomic displacement, and lattice perturbation. This induces three key defect structures in the lattice: oxygen vacancies (V_O), gallium vacancies (V_Ga), and oxygen antisite defects (O_Ga). These defects introduce deep-level trap states in the band gap, which can effectively trap electrons or holes, forming local insulating regions and providing a physical mechanism for improving the overall resistivity of the material.

[0062] Next, the gallium oxide substrate, after proton irradiation treatment, enters the annealing stage. This process is carried out in an inert atmosphere (such as N2 or Ar) or a vacuum environment to avoid oxidation or reduction reactions affecting defect stability. The annealing temperature is set to 400°C to 800°C, and the annealing time is 0.5 hours to 2 hours, with the preferred parameters being 600°C and 1 hour.

[0063] Annealing plays a dual role: firstly, it eliminates some non-target lattice damage caused by irradiation (such as surface stress and interstitial dislocations), restoring crystal order; secondly, it promotes the rearrangement and stabilization of deep-level defect states, enhancing their ability to capture free carriers. This step improves the electrical uniformity, thermal stability, and interfacial compatibility of the material, making it a key thermal activation process for crystal functional transformation. In other words, annealing is used to thermally activate and regulate the gallium oxide crystal structure formed after proton irradiation. Specifically, it involves: using set temperature and time conditions to release some lattice disturbances, structural dislocations, or surface stresses caused by proton injection, thereby improving the crystal's order and structural integrity; and promoting the rearrangement and thermal stabilization of deep-level defect structures in the lattice through thermal diffusion and defect state stabilization processes, enhancing the defect states' ability to capture free carriers.

[0064] This annealing process can further improve the resistivity uniformity, thermal stability, and interface compatibility of gallium oxide crystals in subsequent device processing. It is an indispensable functional step in realizing the transformation of gallium oxide from a conductive state to a semi-insulating state.

[0065] Finally, a gallium oxide substrate that has undergone irradiation and annealing was obtained. A stable distribution of deep-level trap defect structures has been formed in the crystal, the overall free carrier concentration has decreased significantly, the resistivity has increased significantly, and the material exhibits typical semi-insulating properties.

[0066] The "gallium oxide semi-insulating substrate" refers to a gallium oxide crystal material whose electrical properties can be regulated through a lattice defect-induced mechanism without relying on external doping. This substrate possesses excellent resistivity uniformity, thermal stability, and structural integrity, making it suitable as a basic platform for epitaxial growth in applications such as high-frequency devices, power devices, and deep-ultraviolet detectors. Furthermore, its doping-free, contactless, and low-contamination fabrication path significantly improves device compatibility and process versatility, avoiding the poor material uniformity and repeatability issues present in traditional semi-insulating methods.

[0067] The first set of comparative experiments is given below to verify the effectiveness of the method described in this invention. Three sets of unintentionally doped β-Ga2O3 single crystal substrate samples (all with a thickness of 650 μm) were selected for comparative experiments (please refer to Table 1 below, "~" indicates "approximately"): Table 1

[0068] The experimental results above show that: Sample A, without any treatment, exhibits obvious n-type conductivity, high carrier concentration, and low resistivity; Sample B, after being treated under the typical parameter conditions of this application embodiment, shows an increase in resistivity of about 5 orders of magnitude and a decrease in free carrier concentration to near intrinsic level, exhibiting stable semi-insulating properties; Sample C also shows significant electrical improvement under the higher energy and lower dose combination of this application embodiment, proving that this method has good adaptability to different energy windows.

[0069] The results fully verify that by introducing deep-level lattice defects through high-energy proton beams and combining them with annealing to optimize the crystal structure, the resistivity of gallium oxide materials can be effectively improved, enabling the transition from a conductive state to a semi-insulating state, thus meeting the key material requirements of high-frequency and high-voltage devices.

[0070] The second set of comparative experiments will be conducted below. Please refer to Table 2: Table 2

[0071] Based on the results of the second set of comparative experiments, although Fe doping can improve resistivity, it leads to uneven carrier concentration and localized conductivity due to doping inhomogeneity and thermal diffusion. In contrast, the method introduced deep-level defects rather than external impurities, resulting in better stability and uniformity.

[0072] The third set of comparative experiments will be conducted below. Please refer to Table 3: Table 3

[0073] Based on the results of the third set of comparative experiments, the annealing process not only eliminates non-target damage but also stabilizes deep-level trap states, improving the consistency of material properties.

[0074] The fourth set of comparative experiments will now be conducted. Please refer to Table 4 below: Table 4

[0075] Based on the results of the fourth set of comparative experiments, proton irradiation has better energy and controllability, and can effectively control the entire thickness range of the wafer.

[0076] In summary, compared with Fe doping, γ irradiation, or simple irradiation, the "proton irradiation + annealing" scheme adopted in this invention has advantages such as controllable penetration depth, stable defect states, and no external doping contamination. It can effectively achieve a controllable transition from a conductive state to a semi-insulating state while ensuring the integrity of the crystal structure, thereby improving the basic adaptability and mass production reliability of gallium oxide materials in high-voltage and high-frequency devices.

[0077] Compared with traditional methods for realizing gallium oxide semi-insulating substrates, proton irradiation has the following advantages, specifically: (1) Precise control: Proton irradiation is a mature technology that can precisely control the introduction of defects and changes in electrical properties in gallium oxide materials by adjusting parameters such as irradiation energy, dose and irradiation time, so as to achieve the required semi-insulating properties.

[0078] (2) Non-contact treatment: Proton irradiation is a non-contact treatment method that will not cause mechanical damage to the material surface, which is beneficial to maintaining the crystal quality and surface flatness of the material.

[0079] (3) Low cost and high efficiency: Compared with traditional preparation methods, proton irradiation equipment is relatively simple, has a low cost, and can complete the processing in a short time, thus improving production efficiency.

[0080] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0081] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0082] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for preparing a gallium oxide semi-insulating substrate, characterized in that, The method for preparing the gallium oxide semi-insulating substrate includes the following steps: A gallium oxide single crystal substrate of a predetermined thickness is subjected to proton irradiation to introduce lattice defects into the gallium oxide single crystal substrate; The gallium oxide single crystal substrate, into which the lattice defects have been introduced, is subjected to annealing treatment; A gallium oxide semi-insulating substrate is obtained; wherein, the gallium oxide semi-insulating substrate refers to a gallium oxide substrate in a semi-insulating state.

2. The method for preparing a gallium oxide semi-insulating substrate as described in claim 1, characterized in that, The lattice defects include oxygen vacancy defects, gallium vacancy defects, and oxygen antisite defects.

3. The method for preparing a gallium oxide semi-insulating substrate as described in claim 2, characterized in that, The oxygen vacancy defects, gallium vacancy defects, and oxygen antisite defects are formed in the band gap of the gallium oxide single crystal substrate and act as deep-level traps for capturing free charge carriers.

4. The method for preparing a gallium oxide semi-insulating substrate as described in claim 3, characterized in that, The proton irradiation treatment involves an injection energy of 40 to 80 MeV.

5. The method for preparing a gallium oxide semi-insulating substrate as described in claim 4, characterized in that, The proton irradiation treatment dose is 1×10¹ 6 Up to 1×10¹ 8 Ions per square centimeter.

6. The method for preparing a gallium oxide semi-insulating substrate as described in claim 3, characterized in that, The annealing process is performed at a temperature range of 400°C to 800°C for 0.5 to 2 hours.

7. The method for preparing a gallium oxide semi-insulating substrate as described in claim 6, characterized in that, The preset thickness of the gallium oxide single crystal substrate is 200 to 1000 micrometers.

8. The method for preparing a gallium oxide semi-insulating substrate as described in claim 7, characterized in that, The gallium oxide single crystal substrate is unintentionally doped gallium oxide.

9. The method for preparing a gallium oxide semi-insulating substrate as described in claim 8, characterized in that, The step of obtaining the gallium oxide semi-insulating substrate specifically includes: Multiple unit samples are cut from the gallium oxide semi-insulating substrate along the thickness direction.

10. A gallium oxide semi-insulating substrate, characterized in that, It is prepared using the method for preparing gallium oxide semi-insulating substrate as described in any one of claims 1 to 9.

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