A diamond gallium oxide photodetector and a preparation method thereof

Abstract

The application relates to the technical field of photoelectric detectors, and particularly provides a diamond gallium oxide photoelectric detector and a preparation method thereof. The method comprises the following steps: growing a composite film structure on a temporary growth substrate; stripping the composite film structure from the temporary growth substrate; transferring and bonding the composite film structure to a flexible conductive substrate by contacting an n-type gallium nitride film with a conductive layer of the flexible conductive substrate; forming a top electrode on a p-type diamond film to obtain a diamond gallium oxide photoelectric detector adopting a vertical structure; and the bottom electrode of the diamond gallium oxide photoelectric detector is the conductive layer of the flexible conductive substrate. The method can solve the problems that diamond is easily oxidized and degraded under a high-temperature oxygen-rich environment in the preparation technology of an existing diamond gallium oxide heterojunction device, the interface quality is difficult to control, and diamond and gallium oxide are hard and brittle materials and are difficult to be applied to the flexible electronic field.

Description

Technical Field

[0001] This application relates to the field of photodetector technology, and more specifically, to a diamond gallium oxide photodetector and its fabrication method. Background Technology

[0002] Because solar-blind ultraviolet photodetectors based on wide-bandgap semiconductor materials can accurately identify ultraviolet signals in the solar-blind band while filtering out interference from other bands of sunlight, these detectors have irreplaceable application value in many fields.

[0003] Gallium oxide (GaO) has a bandgap corresponding to the solar-blind ultraviolet band and possesses extremely high breakdown field strength and Baliga figure of merit, making it an ideal material for fabricating high-performance solar-blind ultraviolet detectors. Diamond, with its ultra-high carrier mobility, extremely high thermal conductivity, and excellent radiation resistance, has significant advantages in high-power devices, high-temperature devices, and devices used in radiation environments. Since GaO typically exhibits n-type conductivity and p-type doping is extremely difficult, it is challenging to fabricate stable pn junctions through self-doping. Diamond, however, can achieve stable p-type conductivity relatively easily through boron doping. Therefore, combining p-type diamond with n-type GaO to construct a pn heterojunction not only leverages the advantages of both materials to achieve high-performance ultraviolet detection but also utilizes diamond's excellent heat dissipation properties to address the issue of GaO's low thermal conductivity, which hinders heat dissipation during device operation and affects performance stability and lifespan.

[0004] However, diamond and gallium oxide are inherently hard and brittle materials, typically grown on rigid substrates such as sapphire, silicon carbide, or self-supporting substrates, making them difficult to bend or fold directly. This significantly limits their application in flexible electronics. Furthermore, existing diamond-gallium oxide photodetector fabrication techniques and device structures still suffer from the following significant defects and shortcomings: First, directly constructing a diamond-gallium oxide heterojunction requires growing gallium oxide on diamond using methods such as metal-organic chemical vapor deposition. However, gallium oxide growth typically requires a high-temperature and oxygen-rich environment. As an allotrope of carbon, diamond is highly susceptible to oxidation in high-temperature, oxygen-rich environments, generating gaseous carbon oxides. This leads to etching, graphitization, and even burning of the diamond surface. This not only compromises the crystal quality of the diamond but also introduces numerous defects and interface states at the heterojunction interface, significantly increasing the leakage current of the device and reducing the detector's response performance and detection capability.

[0005] Secondly, diamond is a cubic crystal system, while gallium oxide is usually a monoclinic or trigonal crystal system. There is a huge lattice mismatch and difference in thermal expansion coefficient between the two. Gallium oxide films grown directly on the diamond surface are prone to high-density dislocations and cracks, which seriously affect the crystal quality of the film and the optoelectronic performance of the device, thus failing to give full play to the performance advantages of the two materials.

[0006] Finally, existing devices use a planar interdigitated electrode structure. Although this structure is simple to manufacture, the carrier transport path is long and is greatly affected by surface states, resulting in slow device response and large dark current.

[0007] There is currently no effective technical solution to the above problems. Summary of the Invention

[0008] The purpose of this application is to provide a diamond gallium oxide photodetector and its fabrication method, which can solve the problems in the existing diamond gallium oxide heterojunction device fabrication technology, such as the easy oxidation and degradation of diamond in a high temperature and oxygen-rich environment, which makes it difficult to control the interface quality, and the difficulty of applying diamond and gallium oxide as hard and brittle materials to the field of flexible electronics.

[0009] In a first aspect, this application provides a method for fabricating a diamond gallium oxide photodetector, which includes the following steps: S1. A composite thin film structure is grown on a temporary growth substrate; the composite thin film structure includes a p-type diamond film, a buffer barrier film and an n-type gallium oxide film stacked sequentially from bottom to top; S2. Peel the composite thin film structure from the temporary growth substrate; S3. The composite thin film structure is transferred and bonded to the flexible conductive substrate by contacting the n-type gallium oxide thin film with the conductive layer of the flexible conductive substrate. S4. A top electrode is formed on a p-type diamond film to obtain a diamond gallium oxide photodetector with a vertical structure; the bottom electrode of the diamond gallium oxide photodetector is a conductive layer of a flexible conductive substrate.

[0010] Optionally, step S1 includes: S11. The temporary growth substrate is ultrasonically cleaned for a first preset duration using propanol, anhydrous ethanol and deionized water in sequence. S12. Dry the cleaned temporary growth substrate. S13. A p-type diamond film, a buffer barrier film, and an n-type gallium oxide film are sequentially grown on a temporary growth substrate to obtain a composite film structure.

[0011] Optionally, step S13 includes: S131. The temporary growth substrate is placed in a diamond nanopowder suspension and subjected to ultrasonic treatment for a second preset time to form a high-density diamond nucleation center on the surface of the temporary growth substrate. S132. A diamond film is grown on the top surface of a temporary growth substrate, and a p-type doping source is introduced during the film growth process to form a p-type diamond film on the temporary growth substrate. S133. A buffer barrier film is grown on the top surface of a p-type diamond film; S134. Gallium oxide thin film is grown on the top surface of the buffer barrier film, and an n-type doping source is introduced during the film growth process to form an n-type gallium oxide thin film on the buffer barrier film to obtain a composite thin film structure.

[0012] Optionally, step S134 includes: A1. Place the flexible conductive substrate with p-type diamond film and buffer barrier film grown on the stage in the metal-organic chemical vapor deposition reaction chamber. A2. Connect the trimethylgallium gas supply assembly and the water vapor supply assembly to the two independent reaction gas inlet channels of the metal-organic chemical vapor deposition reaction chamber, respectively. A3. Control the metal-organic chemical vapor deposition reaction chamber to grow gallium oxide thin film on the top surface of the buffer barrier film, and introduce an n-type doping source and drive the stage to rotate at a preset speed during the film growth process to form an n-type gallium oxide thin film on the buffer barrier film to obtain a composite thin film structure; the preset speed is 500-1500 revolutions / minute.

[0013] Optionally, the temporary growth substrate is a single-crystal silicon wafer with a crystal orientation of (100). The interfacial bonding force between the temporary growth substrate and the composite thin film structure is less than the interfacial bonding force between the individual films in the composite thin film structure. Step S2 includes: S21. Apply adhesive tape to the top surface of the composite film structure; S22. Apply mechanical peeling force to the composite film structure using adhesive tape to peel the composite film structure from the temporary growth substrate. S23. The composite film structure with adhesive tape is immersed in a pre-prepared piranha solution to remove the tape and adhesive; the piranha solution includes concentrated sulfuric acid solution and hydrogen peroxide solution, with the ratio of concentrated sulfuric acid solution to hydrogen peroxide solution being 3:1; S24. Remove the composite film structure from the piranha solution, and then rinse the composite film structure with deionized water.

[0014] Optionally, step S3 includes: S31. The composite thin film structure is transferred and bonded to the flexible conductive substrate by contacting the n-type gallium oxide thin film with the conductive layer of the flexible conductive substrate using van der Waals forces. S32. Anneal the flexible conductive substrate with the composite thin film structure bonded to it to enhance the interfacial contact between the composite thin film structure and the conductive layer.

[0015] Secondly, this application also provides a gallium diamond oxide photodetector, which is prepared by the gallium diamond oxide photodetector preparation method provided in the first aspect above.

[0016] Optionally, the buffer barrier film is an aluminum nitride film with a thickness of 20-50 nm.

[0017] Optionally, the thickness of the p-type diamond film is 1-3 μm, and the thickness of the n-type gallium oxide film is 200-300 nm.

[0018] Optionally, the carrier concentration of the p-type diamond film is 1×10⁻⁶. 18 cm -3 -1×10 22 cm -3 The carrier concentration of the n-type gallium oxide thin film is 1×10⁻⁶. 18 cm -3 The crystal phase of n-type gallium oxide thin films is α phase.

[0019] As can be seen from the above, the diamond gallium oxide photodetector and its fabrication method provided in this application first grow a composite thin film structure with a buffer barrier film on a temporary growth substrate, and then peel off the composite thin film and transfer bond it to a flexible conductive substrate to finally obtain a vertical architecture device. The buffer barrier film can isolate the high temperature and oxygen-rich environment during the growth process of diamond and gallium oxide, avoid the diamond from being oxidized and damaged, and at the same time buffer the lattice mismatch and thermal mismatch between diamond and gallium oxide, improve the crystal quality of the epitaxial thin film. The vertical architecture shortens the carrier transport path, which can reduce the dark current of the device and improve the response speed. The transfer bonding process realizes the flexibility of the device, adapts to the application requirements of flexible electronic devices, and has the advantages of avoiding diamond oxidation damage, improving the heterojunction interface quality, improving the optoelectronic performance of the device, and adapting to flexible application scenarios. Attached Figure Description

[0020] Figure 1 A flowchart illustrating the fabrication method of a diamond gallium oxide photodetector provided in this application embodiment.

[0021] Figure 2 This is a schematic diagram of the structure of the diamond gallium oxide detector provided in the embodiments of this application.

[0022] Reference numerals: 1. Composite thin film structure; 11. p-type diamond thin film; 12. Buffer barrier film; 13. n-type gallium oxide thin film; 2. Flexible conductive substrate; 3. Top electrode. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0024] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0025] Firstly, such as Figure 1 As shown, this application provides a method for fabricating a diamond gallium oxide photodetector, which includes the following steps: S1. A composite thin film structure 1 is grown on a temporary growth substrate. The composite thin film structure 1 includes a p-type diamond film 11, a buffer barrier film 12 and an n-type gallium oxide film 13 stacked sequentially from bottom to top. S2. Peel the composite thin film structure 1 from the temporary growth substrate; S3. The composite thin film structure 1 is transferred and bonded to the flexible conductive substrate 2 by contacting the n-type gallium oxide thin film 13 with the conductive layer of the flexible conductive substrate 2. S4. A top electrode 3 is formed on a p-type diamond thin film 11 to obtain a diamond gallium oxide photodetector with a vertical structure; the bottom electrode of the diamond gallium oxide photodetector is the conductive layer of the flexible conductive substrate 2.

[0026] For ease of understanding, some key terms in this embodiment are explained below. The diamond gallium oxide photodetector of this embodiment is a device capable of converting optical signals into electrical signals. Its core structure is composed of two semiconductor materials: diamond and gallium oxide, and it is mainly used for detecting ultraviolet light. The temporary growth substrate of this embodiment is a material that serves as a supporting substrate during the semiconductor thin film growth process. Its function is to provide a stable growth surface for the thin film and to be peeled off after the thin film growth is complete so that the thin film can be transferred to other substrates. The composite thin film structure 1 of this embodiment is a structure formed by sequentially stacking thin films of various different materials. In this embodiment, the structure includes a p-type diamond thin film 11, a buffer barrier film 12, and an n-type gallium oxide thin film 13. The p-type diamond thin film 11 of this embodiment is a diamond thin film that exhibits p-type conductivity after doping treatment. P-type doping is usually achieved by introducing boron, which forms holes in the diamond as the main charge carriers. In this embodiment, the buffer barrier film 12 is a thin film located between the p-type diamond film 11 and the n-type gallium oxide film 13. Its function is to isolate the p-type diamond film 11 from the external environment to prevent oxidative degradation of the p-type diamond film 11 in the high-temperature, oxygen-rich environment required for the subsequent formation of the n-type gallium oxide film. Simultaneously, the buffer barrier film 12 serves as a transition layer between the p-type diamond film 11 and the n-type gallium oxide film 13 to alleviate lattice and thermal mismatch between diamond and gallium oxide. In this embodiment, the n-type gallium oxide film 13 is a gallium oxide film exhibiting n-type conductivity after doping treatment. N-type doping is typically achieved by introducing silicon, resulting in electrons as the primary charge carriers in gallium oxide. In this embodiment, the flexible conductive substrate 2 is a flexible substrate material with both flexibility and conductivity, capable of supporting semiconductor devices and providing them with bendable and foldable characteristics. It is commonly used in flexible electronic devices. The flexible conductive substrate 2 is preferably a polyimide flexible film with an indium tin oxide conductive layer on one side, which can serve as the bottom electrode of a diamond-gallium oxide photodetector. In this embodiment, the top electrode 3 is the electrode above the gallium diamond oxide photodetector, and it is in contact with the p-type diamond thin film 11, together forming the electrical path of the device. The vertical architecture of this embodiment is a structural form of the gallium diamond oxide photodetector, in which the bottom electrode of the photodetector, the pn heterojunction (composed of p-type diamond thin film 11 and n-type gallium oxide thin film 13), and the top electrode 3 are stacked in the vertical direction.

[0027] This embodiment provides a method for fabricating a gallium diamond oxide photodetector, which includes the following steps: A composite thin film structure 1 is grown on a temporary growth substrate. This temporary growth substrate can be made of various materials, such as sapphire, silicon carbide, or silicon. Preferably, silicon substrates are commonly used as temporary growth substrates due to their lower cost and ease of fabrication. The composite thin film structure 1 includes, from bottom to top, a p-type diamond film 11, a buffer barrier film 12, and an n-type gallium oxide film 13 stacked sequentially. The p-type diamond film 11 can be grown using methods such as microwave plasma chemical vapor deposition (MPCVD) and doped by introducing a boron source (preferably diborane gas). The buffer barrier film 12 can be grown using techniques such as molecular beam epitaxy (MBE) or atomic layer deposition (ALD), and the buffer barrier film 12 is preferably an aluminum nitride (AlN) film. The n-type gallium oxide film 13 can be grown using methods such as metal-organic chemical vapor deposition (MOCVD) and doped by introducing a silicon source.

[0028] The composite thin film structure 1 is peeled off from the temporary growth substrate. Peeling methods can include mechanical peeling, laser peeling, or chemical etching peeling. For example, if the composite thin film structure is small, adhesive tape can be applied to the top surface of the composite thin film structure 1, and then mechanical force can be applied using the tape to peel the composite thin film structure 1 off from the temporary growth substrate (mechanical peeling). This method has the advantages of simple operation and low peeling cost. If the composite thin film structure is large, laser peeling or chemical etching peeling is required to peel the composite thin film structure 1 off from the temporary growth substrate. This method has the advantage of stable peeling effect.

[0029] The composite thin film structure 1 is transferred and bonded to the flexible conductive substrate 2 by contacting the n-type gallium oxide thin film 13 with the conductive layer of the flexible conductive substrate 2. The flexible conductive substrate 2 can be made of polyimide (PI) film, polyethylene terephthalate (PET) film, or PEN film, etc., and its conductive layer can be indium tin oxide (ITO), silver nanowires, or graphene, etc. After the n-type gallium oxide thin film 13 contacts the conductive layer of the flexible conductive substrate 2, van der Waals forces are generated between the n-type gallium oxide thin film 13 and the conductive layer, which enable bonding between the n-type gallium oxide thin film 13 and the conductive layer of the flexible conductive substrate 2.

[0030] A top electrode 3 is formed on a p-type diamond thin film 11 to obtain a diamond gallium oxide photodetector with a vertical architecture. The bottom electrode of the diamond gallium oxide photodetector is a conductive layer of a flexible conductive substrate 2. The top electrode 3 can be formed by methods such as evaporation, sputtering, or screen printing. The electrode material can be titanium / gold (Ti / Au), nickel / gold (Ni / Au), or aluminum (Al), for example, a Ti / Au metal layer can be evaporated and deposited on the top surface of the p-type diamond thin film 11 as the top electrode 3.

[0031] The following is a more specific example to illustrate the above technical solution in greater detail: In the fabrication process of traditional diamond-gallium oxide heterojunction photodetectors, diamond is easily oxidized and degraded in a high-temperature, oxygen-rich growth environment, resulting in poor heterojunction interface quality; large lattice and thermal mismatches between diamond and gallium oxide lead to poor epitaxial layer quality; and flexible vertical architecture devices suffer from difficulties in electrode contact and ensuring thin film integrity. To address these issues, this application proposes a method for fabricating diamond-gallium oxide photodetectors that effectively solves the above problems.

[0032] For example, suppose a flexible diamond-gallium oxide photodetector needs to be fabricated. First, a composite thin film structure 1 is grown on a temporary growth substrate. This temporary growth substrate can be a single-crystal silicon wafer with a crystal orientation of (100). On the silicon wafer, a p-type diamond film 11 is first grown by microwave plasma chemical vapor deposition (MPCVD) and p-type doping is performed by introducing diborane (B2H6). Subsequently, an aluminum nitride (AlN) film is grown on the p-type diamond film 11 as a buffer barrier film 12 by molecular beam epitaxy (MBE). Finally, an n-type gallium oxide film 13 is grown on the aluminum nitride film by metal-organic chemical vapor deposition (MOCVD) and n-type doping is performed by introducing silane (SiH4). In this process, the aluminum nitride film effectively isolates the diamond from the high-temperature oxygen-rich environment required for subsequent gallium oxide growth, avoiding the oxidative degradation of the diamond. At the same time, as a transition layer, it alleviates the lattice mismatch and thermal mismatch between diamond and gallium oxide, thereby improving the crystal quality of the gallium oxide epitaxial layer and improving the heterojunction interface quality.

[0033] After the composite thin film structure 1 is grown, it is peeled off from the temporary growth substrate. Specifically, an acid-resistant heat-release tape can be adhered to the surface of the n-type gallium oxide thin film 13. Due to the large thermal mismatch stress between diamond and the silicon substrate, the interfacial adhesion is weak. Therefore, the tape can be used to apply mechanical peeling force to peel the entire composite thin film structure 1 off the silicon substrate. Subsequently, the tape with the film attached is immersed in a pre-prepared piranha solution to remove the tape and adhesive, resulting in the self-supporting composite thin film structure 1.

[0034] Next, the composite thin film structure 1 is transferred and bonded to the flexible conductive substrate 2 by contacting the n-type gallium oxide thin film 13 with the conductive layer of the flexible conductive substrate 2. The flexible conductive substrate 2 can be a flexible polyimide (PI) thin film coated with an indium tin oxide (ITO) conductive layer. The n-type gallium oxide thin film 13 side of the peeled-off composite thin film structure 1 is aligned with the ITO side of the PI film and bonded using van der Waals forces. Annealing is then performed to enhance the interface contact. At this point, the ITO layer directly serves as the bottom cathode electrode of the device, eliminating the complex process of fabricating a back electrode, reducing the fabrication difficulty of the flexible vertical structure device, and avoiding potential damage to the film integrity during the fabrication of the back electrode.

[0035] Finally, a top electrode 3 is formed on the p-type diamond thin film 11. For example, a titanium / gold (Ti / Au) metal layer can be deposited by evaporation as the top electrode 3, thereby obtaining a diamond gallium oxide photodetector with a vertical architecture. This vertical architecture shortens the carrier transport path, reduces the influence of surface states during carrier transport, and improves the device's response speed. Simultaneously, relying on the flexible conductive substrate 2, the device possesses bendable and foldable characteristics, meeting the application requirements in the field of flexible electronics.

[0036] The above-described fabrication method effectively solves the problems of diamond oxidation degradation and lattice mismatch by growing the composite thin film structure 1 on a temporary growth substrate and using a buffer barrier film 12 to isolate diamond from the high-temperature oxygen-rich environment. Compared with the traditional method of directly growing gallium oxide on diamond, which leads to the etching and graphitization of the diamond surface, this application significantly improves the heterojunction interface quality and epitaxial layer crystal quality by introducing the buffer barrier film 12. In addition, the composite structure is fixed to the flexible substrate by a peel-off transfer bonding process, and the conductive layer of the flexible conductive substrate 2 is directly used as the bottom electrode, which simplifies the fabrication difficulty of flexible vertical architecture devices and avoids the damage to the film integrity that may be caused by the fabrication of the back electrode in the traditional method. This vertical architecture design shortens the carrier transport path, improves the device response speed, and the flexible substrate gives the device the characteristics of being bendable and foldable, expanding its application in the field of flexible electronics. Therefore, the fabrication method of this application significantly improves the performance and application potential of diamond gallium oxide photodetectors while solving the problems of the prior art.

[0037] In some preferred embodiments, step S1 includes: S11. The temporary growth substrate is ultrasonically cleaned for a first preset duration using propanol, anhydrous ethanol and deionized water in sequence. S12. Dry the cleaned temporary growth substrate. S13. A p-type diamond film 11, a buffer barrier film 12, and an n-type gallium oxide film 13 are sequentially grown on a temporary growth substrate to obtain a composite film structure 1.

[0038] The first preset time is designed to ensure sufficient time for the solvent to fully act on the substrate surface during the cleaning process, effectively removing contaminants. Those skilled in the art can adjust the first preset time according to the degree of substrate contamination, the type of cleaning agent, and the power of the ultrasonic waves. Preferably, the first preset time in this embodiment is 10 minutes. Ultrasonic cleaning utilizes the cavitation effect generated by ultrasound in a liquid to form microbubbles that rapidly burst, generating powerful shock waves and microjets, thereby stripping particulate matter, oil, and organic residues from the substrate surface. This cleaning process can be carried out by immersing the substrate in an ultrasonic cleaning tank containing a cleaning agent. The frequency and power of the cleaning tank can be adjusted according to cleaning requirements; for example, the frequency can be 20-40 kHz, and the power can be 50-200 W. Propanol, anhydrous ethanol, and deionized water are used as cleaning agents to dissolve and remove different types of contaminants. Specifically, propanol is mainly used to dissolve non-polar organic matter, such as oil; anhydrous ethanol is used to dissolve polar organic matter and further remove residual non-polar organic matter; and deionized water is used to rinse away the solvent and water-soluble inorganic salts remaining from the first two steps. The drying process aims to remove residual liquid from the substrate surface after cleaning, preventing the liquid from evaporating during subsequent high-temperature growth, which could introduce impurities or affect film quality. This process can be carried out by purging with high-purity nitrogen or argon, hot air drying, vacuum baking, etc. For example, drying can be done by using a high-purity nitrogen gun or low-temperature baking in a clean oven.

[0039] This solution addresses the issue of impurities such as oil, particulate matter, and residual organic matter adhering to the surface of the temporary growth substrate after processing and storage. These impurities are typically present in the substrate's surface and are subsequently dried. If these impurities are not removed before film growth, the nucleation conditions for subsequent film growth will be disrupted, leading to poor uniformity of the grown film layers, increased crystal defects, and compromised interfacial adhesion stability between the temporary growth substrate and the composite film. This can result in incomplete film removal or premature film detachment during growth. The operational logic of this solution is as follows: First, the dissolving properties of different solvents are used to remove various contaminants from the substrate surface step by step. Propanol, as an organic solvent, effectively dissolves and removes non-polar organic matter, such as oil, from the substrate surface. Next, anhydrous ethanol, as another organic solvent, further dissolves and removes residual polar organic matter and any traces left by propanol. Finally, deionized water is used to thoroughly rinse away any residues of the cleaning agents from the first two steps, as well as water-soluble inorganic impurities, ensuring a highly clean substrate surface. Throughout the cleaning process, the cavitation effect of ultrasound generates microscopic impact force, effectively peeling away firmly attached particulate impurities and achieving a more thorough cleaning effect than conventional cleaning, while avoiding mechanical damage to the substrate surface. After cleaning, the substrate is dried to remove residual moisture, preventing moisture from introducing additional contamination or affecting film quality during subsequent high-temperature film growth. After such thorough cleaning and drying, the surface of the temporary growth substrate becomes clean and flat, providing ideal nucleation conditions for the sequential growth of the p-type diamond film 11, the buffer barrier film 12, and the n-type gallium oxide film 13 in subsequent step S13. The clean substrate surface ensures the uniformity of diamond nucleation, resulting in better crystallization quality of subsequent film layers. At the same time, stable interfacial adhesion is also guaranteed, which not only ensures that the film will not detach prematurely due to insufficient adhesion during growth, but also lays the foundation for the complete peeling of the composite film structure 1 from the temporary growth substrate in subsequent step S2. This pretreatment mechanism, combined with the overall fabrication process of growing composite thin film structure 1 on a temporary growth substrate, peeling, transfer bonding, and forming the top electrode 3, significantly improves the stability and reliability of the entire fabrication process, thereby effectively improving the yield and photoelectric performance of the final diamond gallium oxide photodetector.

[0040] In some preferred embodiments, step S13 includes: S131. The temporary growth substrate is placed in a diamond nanopowder suspension and subjected to ultrasonic treatment for a second preset time to form a high-density diamond nucleation center on the surface of the temporary growth substrate. S132. A diamond film is grown on the top surface of the temporary growth substrate, and a p-type doping source is introduced during the film growth process to form a p-type diamond film 11 on the temporary growth substrate. S133. A buffer barrier film 12 is grown on the top surface of the p-type diamond film 11; S134. Gallium oxide film is grown on the top surface of buffer barrier film 12, and an n-type doping source is introduced during the film growth process to form an n-type gallium oxide film 13 on buffer barrier film 12 to obtain composite film structure 1.

[0041] A temporary growth substrate is subjected to ultrasonic treatment in a diamond nanoparticle suspension (preferably with a particle size of 5-10 nm). The aim is to utilize the cavitation effect and mechanical vibration of ultrasound to promote the uniform adsorption and anchoring of diamond nanoparticles onto the surface of the temporary growth substrate, thereby forming high-density and uniformly distributed diamond nucleation centers. The diamond nanoparticle suspension can be prepared by dispersing diamond nanoparticles with a particle size ranging from several nanometers to tens of nanometers in solvents such as deionized water, ethanol, or isopropanol. Those skilled in the art can adjust the second preset time according to factors such as the material of the temporary growth substrate, the concentration of the diamond nanoparticles, and the power of the ultrasonic equipment. The second preset time is preferably 30 minutes. The ultrasonic treatment in this embodiment can be performed using an ultrasonic cleaner or a dedicated ultrasonic generator.

[0042] A diamond film is grown on the top surface of a temporary growth substrate, and a p-type dopant source is introduced during the film growth process to form a p-type diamond film 11. Diamond film growth can be achieved using techniques such as microwave plasma chemical vapor deposition (MPCVD) and hot-wire chemical vapor deposition (HFCVD). The p-type dopant source is typically a boron-containing gas, such as diborane (B₂H₆) or trimethylborane (TMB). By precisely controlling the flow rate of the dopant source, in-situ doping can be achieved during diamond film growth, ensuring the uniformity and controllability of the doping. The specific formation process of the p-type diamond film 11 is as follows: placing the silicon substrate into the reaction chamber of the microwave plasma chemical vapor deposition (MPCVD) system; evacuating the reaction chamber to a background vacuum level below 10... -3 The reaction mixture was introduced at a torrent rate, using hydrogen (H2) and methane (CH4) as reactants at a flow rate ratio of H2:CH4 = 100:3. The gas pressure was maintained at 75 torr, the microwave power at 7200 W, and the stage temperature at 890°C to initiate diamond film growth. During the growth process, diborane (B2H6) gas was introduced for in-situ light doping, with the B2H6 to CH4 flow rate ratio controlled at approximately 10 ppm. The diamond inkstone growth was continued for 4 hours to obtain a p-type lightly doped layer with a thickness of approximately 2 μm (carrier concentration of 1 × 10⁻⁶) on the silicon substrate (temporary growth substrate).18 cm -3 Up to 1×10 22 cm -3 (Left and right) Polycrystalline diamond film.

[0043] A buffer barrier film 12 is grown on the top surface of the p-type diamond film 11. This film serves as an intermediate layer, effectively isolating the p-type diamond film 11 from the subsequent n-type gallium oxide film 13 growth environment and mitigating lattice and thermal mismatch between them. The buffer barrier film 12 can be made of wide-bandgap semiconductor materials such as aluminum nitride (AlN), aluminum oxide (Al2O3), or silicon nitride (Si3N4), and its growth methods can include molecular beam epitaxy (MBE), atomic layer deposition (ALD), or pulsed laser deposition (PLD). The specific formation process of the buffer barrier film 12 can be as follows: the sample with the p-type diamond film 11 grown is removed and transferred to a molecular beam epitaxy (MBE) system; under ultra-high vacuum conditions (vacuum degree better than 1×10⁻⁶), the sample is grown in a vacuum environment. -9 Using high-purity aluminum as the aluminum source and radio frequency plasma nitrogen as the nitrogen source, the temporary growth substrate was heated to 600°C for thermal cleaning. Then, the temperature of the p-type diamond film 11 was set to 650°C, the aluminum source baffle and the nitrogen source were turned on, and finally the growth rate of the molecular beam epitaxy system was controlled at 0.2 μm / h and the growth time was set to 10 minutes to deposit a 30 nm thick aluminum nitride (AlN) film on the surface of the p-type diamond film 11. This AlN film is dense and continuous to prevent the oxidation of diamond in subsequent high-temperature processes.

[0044] Gallium oxide (GaO) films are grown on the top surface of the buffer barrier film 12, and an n-type dopant source is introduced during the film growth process to form an n-type GaO film 13. GaO film growth can be achieved using methods such as metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or pulsed laser deposition (PLD). The n-type dopant source is typically a silicon-containing gas, such as silane (SiH4) or disilane (Si2H6), or it can be a sulfur-containing gas, such as hydrogen sulfide (H2S). By simultaneously introducing the dopant source during the growth process, n-type doping can be achieved, ensuring the conductivity of the film. The specific formation process of the n-type gallium oxide thin film 13 can be as follows: A temporary growth substrate with a p-type diamond thin film 11 and a buffer barrier film 12 grown on it is transferred to a metal-organic chemical vapor deposition (MOCVD) reaction chamber; trimethylgallium (TMGa) is used as the gallium source for MOCVD, water (H2O) as the oxygen source, silane (SiH4) as the n-type doping source, and argon (Ar) as the carrier gas; the temperature of the reaction chamber base is set between 430℃ and 470℃ (this temperature range is lower than that used with oxygen to ensure α-phase purity); TMGa is introduced at a flow rate of 15-20 μmol / min, and the H2O source carrier gas flow rate is 50-100 sccm (the water bath temperature is controlled at a constant 20℃), while a trace amount of SiH4 is introduced simultaneously to achieve n-type doping (carrier concentration controlled at 1×10⁻⁶). 18 cm -3 (Approximately). Growth was carried out at 450℃ for 90 minutes to obtain high-quality, smooth-surfaced n-type Ga2O3 films with an α-phase crystal orientation and a thickness of 200-300 nm.

[0045] This scheme, by clearly defining the complete growth process of each layer of the composite thin film structure 1 from substrate pretreatment to final film formation, can effectively improve the crystallinity of each layer of the thin film and optimize the interface quality of the heterojunction, providing a good structural foundation for the fabrication of high-performance diamond gallium oxide photodetectors. The temporary growth substrate is placed in a diamond nanopowder suspension for ultrasonic treatment. The ultrasonic action allows diamond nanoparticles to uniformly adhere to the substrate surface, forming high-density and uniformly distributed diamond nucleation centers. This provides uniform growth sites for the subsequent growth of the p-type diamond thin film 11, avoiding problems such as uneven grain size and poor crystallinity during diamond film growth, and ensuring the growth quality of the p-type diamond thin film 11. When growing the diamond thin film on the top surface of the substrate, a p-type doping source is introduced simultaneously during the growth process, achieving simultaneous film growth and doping. This ensures the uniformity of p-type doping, resulting in a p-type diamond thin film 11 that meets conductivity requirements, while eliminating the need for subsequent additional doping steps, avoiding damage to the already formed film and substrate from additional processing, and simplifying the overall fabrication process. A buffer barrier film 12 is grown on the top surface of the p-type diamond film 11. The buffer barrier film 12 serves two purposes: firstly, it isolates the p-type diamond from the direct contact between the high-temperature, oxygen-rich growth environment and the p-type diamond during the subsequent growth of the n-type layer, preventing oxidative degradation of the diamond under these conditions and protecting its crystal quality; secondly, it buffers the lattice and thermal mismatch between the p-type diamond and the n-type gallium oxide, reducing the generation of defects such as dislocations and cracks at the heterojunction interface and effectively improving the interface bonding quality of the heterojunction. Finally, while growing the gallium oxide film on the top surface of the buffer barrier film 12, an n-type dopant source is simultaneously introduced, achieving simultaneous growth and doping, ensuring the uniformity of the n-type doping, and obtaining an n-type gallium oxide film 13 that meets the conductivity requirements. Ultimately, a fully stacked and high-quality composite film structure 1 is obtained, laying a solid foundation for the subsequent fabrication of high-performance photodetectors.

[0046] In some preferred embodiments, step S134 includes: A1. Place the flexible conductive substrate 2, on which the p-type diamond film 11 and the buffer barrier film 12 are grown, onto the stage in the metal-organic chemical vapor deposition reaction chamber. A2. Connect the trimethylgallium gas supply assembly and the water vapor supply assembly to the two independent reaction gas inlet channels of the metal-organic chemical vapor deposition reaction chamber, respectively. A3. Control the metal-organic chemical vapor deposition reaction chamber to grow gallium oxide film on the top surface of buffer barrier film 12, and introduce n-type doping source and drive the stage to rotate at a preset speed during the film growth process to form n-type gallium oxide film 13 on buffer barrier film 12 to obtain composite film structure 1; the preset speed is 500-1500 revolutions / minute.

[0047] A metal-organic chemical vapor deposition (MOCVD) reaction chamber is an apparatus used for thin film epitaxial growth. Its internal environment allows for precise control of temperature, pressure, and gas flow rate to achieve high-quality film fabrication. The stage inside the reaction chamber holds the substrate to be grown and allows for heating and rotation. A trimethylgallium (TMGa) gas supply assembly provides the gallium source, for example, by controlling the cylinder pressure and flow rate to deliver high-purity TMG gas to the reaction chamber. A water vapor supply assembly provides the oxygen source, for example, by heating deionized water to generate water vapor, which is then delivered to the reaction chamber as a carrier gas. The design of connecting the TMG gas supply assembly and the water vapor supply assembly to two independent reaction gas inlet channels of the MOCVD reaction chamber aims to prevent pre-reaction of the source gases before they enter the reaction chamber, thereby reducing impurity formation and improving film quality. For example, the spray head at the top of the MOCVD reaction chamber is designed with a double-layered channel that does not communicate with each other; the upper channel is used to introduce TMGa and its carrier gas (Ar), and the lower channel is used to introduce H2O vapor and its carrier gas.

[0048] Driving the stage to rotate at a preset speed refers to continuously rotating the stage during film growth using mechanical or magnetic levitation methods. This ensures that all areas of the substrate surface are uniformly exposed to the reactive gases and dopant sources, thereby improving the thickness and doping uniformity of the film. The preset speed range is 500-1500 revolutions per minute. When the stage rotates at the preset speed, it acts like a powerful exhaust fan, generating a downward suction force that instantly draws the reactive gases overhead towards the surface of the buffer barrier film 12. This minimizes the time the reactive gases spend in mid-air, further preventing pre-reaction of the source gases.

[0049] This solution effectively addresses the film quality issue caused by uneven gas distribution during the growth of n-type gallium oxide thin films 13 through optimized metal-organic chemical vapor deposition (MOCVD) processes. First, a flexible conductive substrate 2, with p-type diamond thin films 11 and buffer barrier films 12 grown on it, is precisely placed on the stage within the MOCVD reaction chamber, providing a stable and controllable reaction environment for subsequent film growth. Second, by connecting the trimethylgallium gas supply assembly and the water vapor supply assembly to two independent reaction gas inlet channels, unnecessary pre-reactions of the gallium and oxygen sources before entering the reaction chamber are prevented, effectively suppressing impurity generation and ensuring the purity of the reaction process. This lays the foundation for the formation of high-quality gallium oxide thin films. Building upon this foundation, during the gallium oxide thin film growth process, not only was an n-type dopant source introduced to precisely control the film's conductivity, but more importantly, the stage was driven to rotate at a preset speed (500-1500 revolutions / minute). This rotation mechanism further reduced the occurrence of pre-reactions between the gallium and oxygen sources and ensured uniform contact between the substrate surface and the reaction source gas and dopant source, thereby significantly improving the thickness uniformity, crystal quality, and n-type dopant distribution uniformity of the gallium oxide thin film. Through these synergistic effects, this scheme ensures that the grown n-type gallium oxide thin film 13 meets the fabrication requirements of heterojunction photodetectors, providing a solid foundation for the performance stability and reliability of subsequent diamond gallium oxide photodetectors.

[0050] In some preferred embodiments, the temporary growth substrate is a single-crystal silicon wafer with a crystal orientation of (100), and the interfacial bonding force between the temporary growth substrate and the composite thin film structure 1 is less than the interfacial bonding force between the thin films in the composite thin film structure 1. Step S2 includes: S21. Apply adhesive tape to the top surface of composite film structure 1; S22. Apply mechanical peeling force to the composite film structure 1 using adhesive tape to peel the composite film structure 1 from the temporary growth substrate. S23. The composite film structure 1 with the adhesive tape attached is immersed in a pre-prepared piranha solution to remove the tape and adhesive; the piranha solution includes concentrated sulfuric acid solution and hydrogen peroxide solution, and the ratio of concentrated sulfuric acid solution to hydrogen peroxide solution is 3:1; S24. Remove the composite film structure 1 from the piranha solution, and then rinse the composite film structure 1 with deionized water.

[0051] A single-crystal silicon wafer with a crystal orientation of (100) is selected as the temporary growth substrate. This silicon wafer has excellent surface symmetry, which is beneficial to improving the crystal quality and surface flatness of the epitaxial diamond film. In addition, the interfacial bonding force between this silicon wafer and the p-type diamond film 11 is less than the interfacial bonding force between the films in the composite film structure 1. Therefore, selecting a single-crystal silicon wafer with a crystal orientation of (100) as the temporary growth substrate is beneficial to achieving non-destructive physical peeling of the composite film structure 1 by mechanical force in subsequent steps. Interfacial bonding force refers to the strength of the interaction between two adjacent material layers. In this scheme, by controlling the material selection of the temporary growth substrate, the bonding force between it and the composite film structure 1 is made relatively weak. This weak bonding force is the key to achieving effective peeling. It ensures that when the peeling force is applied, the separation occurs between the temporary growth substrate and the composite film, rather than between the layers inside the composite film.

[0052] The purpose of attaching adhesive tape to the top surface of the composite film structure 1 is to provide an interface and force point for subsequent mechanical peeling. The tape adheres firmly to the top surface of the composite film structure 1, thereby uniformly transmitting the peeling force to the entire film structure when external force is applied. This tape is preferably an existing acid-resistant heat-release tape or a high-strength polyimide tape. Mechanical peeling force is applied to the composite film structure 1 using the tape to peel it from the temporary growth substrate. This mechanical peeling force refers to the force that acts directly on the tape through physical means, thereby causing the composite film structure 1 to separate from the temporary growth substrate. This peeling method utilizes the relatively weak interfacial bonding between the temporary growth substrate and the composite film structure 1, and the entire film can be transferred through simple mechanical operations. The application of mechanical peeling force can include manual pulling or precise control of peeling using an automated robotic arm.

[0053] The composite film structure 1, with adhesive tape adhered to it, is immersed in a pre-prepared piranha solution to remove the tape and adhesive. Piranha solution is a strong oxidizing mixture commonly used to remove organic residues and clean semiconductor surfaces. Its main components are concentrated sulfuric acid solution (preferably 98% H2SO4 by mass) and hydrogen peroxide solution (preferably 30% H2O2 by mass) mixed in a 3:1 ratio. This mixture generates a large number of free radicals, effectively decomposing and corroding organic materials, such as the polymer substrate and adhesive of the tape. This strong oxidizing cleaning method thoroughly removes any organic contaminants that may remain after the stripping process, ensuring the cleanliness of the composite film structure 1. After treatment with the piranha solution, corrosive solution and decomposition products remain on the surface of the composite film structure 1. Rinsing the composite film structure 1 with deionized water thoroughly removes these residues, preventing further corrosion or contamination and ensuring the surface cleanliness of the film and compatibility with subsequent processes. Deionized water has extremely high purity and effectively removes ionic impurities. The rinsing process can employ various methods such as soaking, spraying, or ultrasonic-assisted rinsing, and can be repeated multiple times to ensure thorough cleaning.

[0054] This solution achieves complete and clean peeling of the composite thin film structure 1 by carefully selecting temporary growth substrate materials, optimizing interface adhesion control, employing mechanically assisted peeling, and using an efficient post-processing cleaning method. Specifically, this solution first selects a single-crystal silicon wafer with a crystal orientation of (100) as the temporary growth substrate, so that the interface adhesion between the substrate and the composite thin film structure 1 is significantly less than the adhesion between the thin film layers inside the composite thin film structure 1. This differentiated adhesion design is the basis for achieving non-destructive peeling. It ensures that when external force is applied, the separation interface occurs preferentially between the temporary growth substrate and the composite film, thereby effectively avoiding cracking or delamination inside the composite film. During the peeling operation, adhesive tape is pasted on the top surface of the composite thin film structure 1 to provide a uniform and controllable force carrier for applying mechanical peeling force. Subsequently, the mechanical peeling force is applied to the composite thin film structure 1 using this adhesive tape, and the composite thin film structure 1 can be peeled off from the temporary growth substrate as a whole. This mechanical peeling method is simple to operate, and due to the pre-design of the interface adhesion, it can achieve efficient and complete film transfer. After peeling, to thoroughly remove the tape and any remaining adhesive, the composite film structure 1 with the tape attached is immersed in a pre-prepared piranha solution. This piranha solution is a specific mixture of concentrated sulfuric acid solution and hydrogen peroxide solution in a 3:1 ratio, which can efficiently decompose and remove the organic components and adhesive of the tape. Simultaneously, this ratio of piranha solution has good compatibility with the semiconductor material in the composite film structure 1 and will not cause damage. Finally, the composite film structure 1 is thoroughly rinsed with deionized water to remove any residues and decomposition products of the piranha solution, ensuring a highly clean surface and laying a good foundation for subsequent processes such as bonding to the flexible conductive substrate 2 and electrode formation. This approach, combined with the method for fabricating diamond gallium oxide photodetectors, ensures, through this controlled peeling and cleaning process, that the composite film structure 1, composed of a p-type diamond film 11, a buffer barrier film 12, and an n-type gallium oxide film 13, maintains its excellent crystal quality and structural integrity after being peeled from the temporary growth substrate. This is crucial for the subsequent transfer and bonding of the composite thin film structure 1 to the flexible conductive substrate 2, ultimately forming a vertically structured diamond gallium oxide photodetector. A complete thin film structure and a clean surface ensure good interfacial contact between the composite thin film and the flexible conductive substrate 2, reducing interface defects and thus improving the electrical performance and reliability of the detector. Especially in flexible applications, the integrity of the thin film directly affects the device's bending life and stability.

[0055] In some preferred embodiments, step S3 includes: S31. The composite thin film structure 1 is transferred and bonded to the flexible conductive substrate 2 by contacting the n-type gallium oxide thin film 13 with the conductive layer of the flexible conductive substrate 2 using van der Waals forces. S32. Anneal the flexible conductive substrate 2 to which the composite thin film structure 1 is bonded to enhance the interfacial contact between the composite thin film structure 1 and the conductive layer.

[0056] Step S31 refers to using van der Waals forces, a non-covalent, weak interaction force, to initially bond the peeled composite thin film structure 1 (on the n-type gallium oxide thin film 13 side) to the conductive layer of the flexible conductive substrate 2. Van der Waals forces are a common intermolecular attraction; although relatively weak, their strength is sufficient to provide adequate initial adhesion for thin film materials with smooth and clean surfaces. The advantage of this bonding method lies in its spontaneity and non-damaging nature. It eliminates the need for additional adhesives or the application of high temperature and pressure, thus avoiding damage to the fragile composite thin film structure 1 or the introduction of an impurity layer, ensuring interface cleanliness and film integrity.

[0057] Step S32 refers to the heat treatment of the entire flexible conductive substrate 2 and the composite thin film structure 1 bonded thereon after the initial bonding is completed. Annealing, by providing heat energy, promotes the diffusion and rearrangement of atoms or molecules at the interface, thereby eliminating interface voids, reducing interface stress, and enhancing the physical or chemical bonding strength between interfaces. This heat treatment can significantly improve the bonding tightness between the composite thin film structure 1 and the conductive layer, reduce contact resistance, and enhance the overall structural stability.

[0058] This solution employs a two-step process to sequentially complete preliminary bonding and contact enhancement treatment, ensuring the bonding quality between the composite film and the conductive layer of the flexible conductive substrate 2, thus meeting the requirements for flexible device applications. The first step utilizes van der Waals forces for bonding. Bonding is achieved through the naturally occurring van der Waals forces between the n-type gallium oxide film 13 and the conductive layer of the flexible conductive substrate 2. This eliminates the need for additional adhesive materials, avoids introducing excess impurities that could affect conductivity, and prevents damage to the already debonded, fragile composite film structure 1 caused by high-temperature, high-pressure, or other high-intensity bonding processes, ensuring the structural integrity of the film itself. Simultaneously, this method allows direct contact between the n-type gallium oxide film 13 and the conductive layer, ensuring that the conductive layer, acting as the bottom electrode, can form a smooth conductive path with the n-type layer, meeting the conductivity requirements of vertical architecture devices. The second step involves annealing the preliminarily bonded composite film. This process promotes further molecular diffusion at the interface between the composite film and the conductive layer, eliminating voids and internal stress at the interface, improving the tightness of the interface bonding, effectively reducing contact resistance, and enhancing the overall stability of the bonding. This prevents film delamination during subsequent processing and flexible application. This step-by-step processing method enhances the interfacial contact effect without compromising the original crystal quality of the composite film, ensuring the performance and structural stability of the device and providing a reliable process foundation for the fabrication of high-performance flexible diamond gallium oxide photodetectors.

[0059] Secondly, this application also provides a gallium diamond oxide photodetector, which is prepared by the gallium diamond oxide photodetector preparation method provided in the first aspect above.

[0060] The diamond gallium oxide photodetector provided in this embodiment is prepared by the diamond gallium oxide photodetector preparation method provided in the first aspect above. The principle of the diamond gallium oxide photodetector provided in this embodiment is the same as that of the diamond gallium oxide photodetector preparation method provided in the first aspect above, and will not be repeated here.

[0061] In some preferred embodiments, the buffer barrier film 12 is an aluminum nitride film with a thickness of 20-50 nm. Aluminum nitride is a wide bandgap semiconductor material with a hexagonal wurtzite structure, stable chemical properties, high temperature resistance, and a certain degree of lattice structure compatibility with diamond and gallium oxide. As a buffer barrier film 12, its main function is to isolate the underlying p-type diamond film 11, preventing it from being oxidized or graphitized in the high-temperature, oxygen-rich environment during the subsequent growth of the n-type gallium oxide film 13. Simultaneously, the aluminum nitride film also serves as a lattice transition layer, mitigating lattice and thermal mismatches between the p-type diamond film 11 and the n-type gallium oxide film 13. The thickness of the aluminum nitride film is 20-50 nm, referring to its vertical dimension. This thickness range is designed to ensure that the aluminum nitride film effectively blocks oxygen diffusion, adequately buffers lattice and thermal mismatches, and avoids increasing the resistance of the carrier transport path due to excessive thickness, thereby affecting the electrical performance of the device. Thin film thickness can be achieved by precisely controlling growth parameters, such as growth rate, growth time, and reactant flow rate. In some preferred embodiments, the thickness of the p-type diamond film 11 is 1-3 μm, and the thickness of the n-type gallium oxide film is 200-300 nm.

[0062] This approach precisely limits the thickness of the p-type diamond film 11 and the n-type gallium oxide film, enabling the fabricated gallium oxide diamond photodetector to achieve high-performance photodetection while maintaining excellent flexibility. Specifically, controlling the thickness of the p-type diamond film 11 within the range of 1-3 μm ensures the formation of a continuous p-type conductive layer with good crystal quality, providing a stable foundation for the construction of the heterojunction and guaranteeing effective absorption of ultraviolet light. Simultaneously, this thickness range avoids increased device rigidity due to excessive film thickness, thus maintaining device flexibility. Building upon this, limiting the thickness of the n-type gallium oxide film to the range of 200-300 nm ensures the crystal quality and integrity of the gallium oxide film, forming a stable n-type functional layer. More importantly, this thickness range optimizes the transport path of photogenerated carriers, effectively reducing the recombination probability during transport and thus improving the collection efficiency of photogenerated carriers. This synergistic optimization in thickness enables the detector to balance flexibility requirements, crystal quality, light absorption efficiency, and carrier collection efficiency in a vertical architecture, thereby effectively solving the rigidity problem of traditional devices in flexible applications and the problem of photoelectric performance degradation caused by improper film thickness.

[0063] In some preferred embodiments, the carrier concentration of the p-type diamond film 11 is 1 × 10⁻⁶. 18 cm -3 -1×10 22 cm -3 The carrier concentration of the n-type gallium oxide thin film is 1×10⁻⁶. 18 cm -3 The crystal phase of n-type gallium oxide thin films is α phase.

[0064] Carrier concentration is the number density of freely moving charge carriers in a semiconductor material, and it directly affects the conductivity of the material and the electrical characteristics of the device. For p-type diamond thin film 11, its carrier concentration can be controlled at 1×10⁻⁶. 18 cm -3 -1×10 22 cm -3 The range is set to ensure that the p-type diamond film 11 has sufficient conductivity to form an effective pn junction, while avoiding the introduction of excessive lattice defects due to excessive doping concentration, which would affect the crystal quality and carrier mobility of the material. This carrier concentration range can be achieved by introducing a p-type dopant, such as boron, during diamond growth, and precisely adjusting the carrier concentration by controlling the dopant flux or concentration. The carrier concentration of the n-type gallium oxide film refers to the number density of free electrons within it; its carrier concentration is set to 1 × 10⁻⁶. 18 cm -3The aim is to achieve a good match with the carrier concentration of the p-type diamond thin film 11 to optimize the built-in electric field distribution of the pn heterojunction. A suitable carrier concentration can ensure that the heterojunction has a wide depletion region under reverse bias, thereby improving the collection efficiency of photogenerated carriers and reducing dark current. This carrier concentration can be achieved by introducing an n-type dopant, such as silicon or tin, during the growth of the gallium oxide thin film, and adjusting it by precisely controlling the dopant flux or source concentration. Alpha-phase gallium oxide is a wide bandgap semiconductor material with a corundum structure. Its crystal phase is defined as alpha phase based on its unique physical and electrical properties. Alpha-phase gallium oxide has a wide bandgap of about 5.3 eV, which makes it very suitable for solar-blind ultraviolet detection applications. In addition, its corundum structure has good lattice matching with a variety of substrate materials (such as sapphire), which is beneficial for achieving high-quality epitaxial growth and reducing the defect density in the thin film. To achieve the growth of α-phase gallium oxide thin films, techniques such as metal-organic chemical vapor deposition or pulsed laser deposition can be used. By precisely controlling parameters such as growth temperature, reactive gas flow rate, substrate type, and atmospheric conditions, the thin film can be induced to grow in an α-phase crystal structure.

[0065] This scheme constructs a pn heterojunction with optimized performance by precisely controlling the carrier concentrations of the p-type diamond film 11 and the n-type gallium oxide film, as well as the crystal phase of the n-type gallium oxide film. Specifically, the carrier concentration of the p-type diamond film 11 is set at 1×10⁻⁶. 18 cm -3 -1×10 22 cm -3 Within this range, the p-type diamond was ensured to have good conductivity, and sufficient hole concentration was provided for the heterojunction. Simultaneously, the carrier concentration of the n-type gallium oxide film was precisely controlled within 1 × 10⁻⁶. 18 cm -3This allows for an ideal match in carrier concentration between the p-type diamond film 11 and the n-type gallium oxide film. This match is crucial for forming a rationally distributed built-in electric field, which effectively separates photogenerated electron-hole pairs and guides them to their respective electrodes, thereby improving the response speed and quantum efficiency of the photodetector. Furthermore, defining the crystal phase of the n-type gallium oxide film as α-phase is based on its superiority in solar-blind ultraviolet detection. α-phase gallium oxide possesses the largest bandgap of all gallium oxide crystal phases, resulting in higher sensitivity to solar-blind ultraviolet light and lower intrinsic dark current. More importantly, the corundum structure of α-phase gallium oxide exhibits good lattice matching with various substrate materials (such as sapphire or aluminum nitride buffer layers), enabling the production of high-quality, low-defect-density epitaxial films during growth. High-quality films significantly reduce defect states at heterojunction interfaces, thereby reducing interfacial recombination losses, further optimizing the transport efficiency of photogenerated carriers, and effectively suppressing device leakage current. Through the synergistic optimization of carrier concentration and crystal phase, this detector can fully utilize the high thermal conductivity and p-type electrical conductivity of p-type diamond, as well as the ultra-wide bandgap and excellent ultraviolet response characteristics of n-type α-phase gallium oxide. Together, it overcomes the problems in traditional diamond / gallium oxide heterojunction devices caused by carrier concentration mismatch or improper crystal phase selection, such as unreasonable built-in electric field, low efficiency of photogenerated carrier separation and transport, and limited device performance, thereby achieving high-performance solar-blind ultraviolet detection.

[0066] As can be seen from the above, the diamond gallium oxide photodetector and its fabrication method provided in this application first grow a composite thin film structure 1 with a buffer barrier film 12 on a temporary growth substrate, and then peel off the composite thin film and transfer bond it to a flexible conductive substrate 2 to finally obtain a vertical architecture device. The buffer barrier film 12 can isolate the high temperature and oxygen-rich environment during the growth process of diamond and gallium oxide, avoid the diamond from being oxidized and damaged, and at the same time buffer the lattice mismatch and thermal mismatch between diamond and gallium oxide, improve the crystal quality of the epitaxial film. The vertical architecture shortens the carrier transport path, which can reduce the dark current of the device and improve the response speed. The transfer bonding process realizes the flexibility of the device, adapts to the application requirements of flexible electronic devices, and has the advantages of avoiding diamond oxidation damage, improving the heterojunction interface quality, improving the optoelectronic performance of the device, and adapting to flexible application scenarios.

[0067] In the embodiments provided in this application, it should be understood that relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0068] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for fabricating a diamond gallium oxide photodetector, characterized in that, The method for fabricating the diamond gallium oxide photodetector includes the following steps: S1. A composite thin film structure is grown on a temporary growth substrate; the composite thin film structure includes a p-type diamond film, a buffer barrier film and an n-type gallium oxide film stacked sequentially from bottom to top, wherein the buffer barrier film is an aluminum nitride film and the thickness of the aluminum nitride film is 20-50 nm. S2. Peel the composite thin film structure off the temporary growth substrate; S3. The composite film structure is transferred and bonded to the flexible conductive substrate by contacting the n-type gallium oxide film with the conductive layer of the flexible conductive substrate. S4. A top electrode is formed on the p-type diamond film to obtain a diamond gallium oxide photodetector with a vertical structure; the bottom electrode of the diamond gallium oxide photodetector is the conductive layer of the flexible conductive substrate.

2. The method for fabricating a diamond gallium oxide photodetector according to claim 1, characterized in that, Step S1 includes: S11. The temporary growth substrate is ultrasonically cleaned for a first preset duration using propanol, anhydrous ethanol and deionized water in sequence. S12. Dry the cleaned temporary growth substrate. S13. A p-type diamond film, a buffer barrier film, and an n-type gallium oxide film are sequentially grown on the temporary growth substrate to obtain a composite film structure.

3. The method for fabricating a diamond gallium oxide photodetector according to claim 2, characterized in that, Step S13 includes: S131. The temporary growth substrate is placed in a diamond nanopowder suspension and subjected to ultrasonic treatment for a second preset duration to form a high-density diamond nucleation center on the surface of the temporary growth substrate. S132. A diamond film is grown on the top surface of the temporary growth substrate, and a p-type doping source is introduced during the film growth process to form a p-type diamond film on the temporary growth substrate. S133. A buffer barrier film is grown on the top surface of the p-type diamond film; S134. Gallium oxide thin film is grown on the top surface of the buffer barrier film, and an n-type doping source is introduced during the film growth process to form an n-type gallium oxide thin film on the buffer barrier film to obtain a composite thin film structure.

4. The method for fabricating a diamond gallium oxide photodetector according to claim 3, characterized in that, Step S134 includes: A1. Place the flexible conductive substrate on which the p-type diamond film and the buffer barrier film are grown on the stage in the metal-organic chemical vapor deposition reaction chamber. A2. Connect the trimethylgallium gas supply assembly and the water vapor supply assembly to the two independent reaction gas inlet channels of the metal-organic chemical vapor deposition reaction chamber, respectively. A3. Control the metal-organic chemical vapor deposition reaction chamber to grow gallium oxide film on the top surface of the buffer barrier film, and introduce an n-type doping source and drive the stage to rotate at a preset speed during the film growth process to form an n-type gallium oxide film on the buffer barrier film to obtain a composite film structure; the preset speed is 500-1500 revolutions / minute.

5. The method for fabricating a diamond gallium oxide photodetector according to claim 1, characterized in that, The temporary growth substrate is a single-crystal silicon wafer with a crystal orientation of (100). The interfacial bonding force between the temporary growth substrate and the composite thin film structure is less than the interfacial bonding force between the individual thin films in the composite thin film structure. Step S2 includes: S21. Adhesive tape is pasted onto the top surface of the composite film structure; S22. Apply a mechanical peeling force to the composite film structure using the tape to peel the composite film structure off from the temporary growth substrate; S23. The composite film structure with the tape attached is immersed in a pre-prepared piranha solution to remove the tape and adhesive; the piranha solution includes a concentrated sulfuric acid solution and a hydrogen peroxide solution, wherein the ratio of the concentrated sulfuric acid solution to the hydrogen peroxide solution is 3:

1. S24. Remove the composite film structure from the piranha solution, and then rinse the composite film structure with deionized water.

6. The method for fabricating a diamond gallium oxide photodetector according to claim 1, characterized in that, Step S3 includes: S31. The composite thin film structure is transferred and bonded to the flexible conductive substrate by contacting the n-type gallium oxide thin film with the conductive layer of the flexible conductive substrate using van der Waals forces. S32. Anneal the flexible conductive substrate with the composite thin film structure bonded thereon to enhance the interfacial contact between the composite thin film structure and the conductive layer.

7. A diamond gallium oxide photodetector, characterized in that, The diamond gallium oxide photodetector is prepared by the diamond gallium oxide photodetector preparation method according to any one of claims 1-6.

8. The diamond gallium oxide photodetector according to claim 7, characterized in that, The thickness of the p-type diamond film is 1-3 μm, and the thickness of the n-type gallium oxide film is 200-300 nm.

9. The diamond gallium oxide photodetector according to claim 7, characterized in that, The carrier concentration of the p-type diamond film is 1×10⁻⁶. 18 cm −3 -1×10 22 cm −3 The carrier concentration of the n-type gallium oxide thin film is 1×10⁻⁶. 18 cm −3 The crystal phase of the n-type gallium oxide thin film is the α phase.

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