STO-Ga2O3 heterojunction-based solar-blind ultraviolet photoelectric detector and preparation method thereof
By fabricating Ga2O3 heterojunctions on strontium titanate (STO) single-crystal substrates, the performance bottleneck of β-Ga2O3-based photodetectors caused by lattice mismatch was solved, realizing a solar-blind ultraviolet photodetector with low dark current, high detectivity and fast response.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-24
- Publication Date
- 2026-04-07
AI Technical Summary
Existing β-Ga2O3-based photodetectors suffer from high-density through-dislocations and residual stress due to lattice mismatch and differences in thermal expansion coefficients between the sapphire substrate and β-Ga2O3, resulting in high dark current and limited responsivity and detectivity.
Using a strontium titanate (STO) single crystal substrate and a Ga2O3 heterojunction, gallium oxide thin films were deposited by magnetron sputtering and followed by annealing to prepare interdigitated electrodes, forming a type I band-aligned heterojunction.
A solar-blind ultraviolet photodetector with low dark current, high detectivity and fast response was achieved. It has a smooth surface, high crystal quality, dark current as low as 2.1×10-12A, light-dark-current ratio as high as 105, responsivity as high as 0.23 A/W, and detectivity of 1.93×1013 Jones.
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Figure CN121815786A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor optoelectronic device technology, specifically relating to a solar-blind ultraviolet photodetector based on STO-Ga2O3 heterojunction and its fabrication method. Background Technology
[0002] Solar-blind ultraviolet photodetectors have attracted much attention due to their significant application value in military and civilian fields such as missile early warning, flame detection, and non-line-of-sight communication. Gallium oxide (β-Ga2O3), as an emerging ultrawide bandgap semiconductor (~4.9 eV), has an intrinsic absorption edge located in the solar-blind band (~280 nm), making it an ideal material for fabricating solar-blind detectors.
[0003] Currently, sapphire (c-Al2O3) is often used as the epitaxial substrate in β-Ga2O3-based photodetectors. However, there is a large lattice mismatch and difference in thermal expansion coefficient between sapphire and β-Ga2O3. This usually introduces a high density of penetrating dislocations and residual stress at the heteroepitaxial interface, which become carrier scattering and recombination centers, ultimately leading to performance bottlenecks such as high dark current, limited responsivity, and limited detectivity.
[0004] Strontium titanate (SrTiO3, STO) single crystals, as a perovskite oxide, exhibit good lattice matching with many high-temperature superconducting materials and possess advantages such as high dielectric constant, low dielectric loss, and good thermal stability. Therefore, STO is currently the most widely used substrate material in the field of high-temperature superconducting thin film growth. However, there are currently no reports on the epitaxial growth of Ga2O3 thin films on STO substrates and their ultraviolet detection performance. Summary of the Invention
[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the main objective of this invention is to provide a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction, characterized by low dark current, high detectivity, high photocurrent-to-dark-current ratio, and fast response speed.
[0006] The present invention also provides a method for fabricating the solar-blind ultraviolet photodetector based on the STO-Ga2O3 heterojunction.
[0007] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction, comprising the following steps: 1) Gallium oxide thin films were deposited on strontium titanate substrates using magnetron sputtering; 2) The deposited gallium oxide film is post-annealed in an inert atmosphere; 3) Prepare metal interdigitated electrodes on the surface of the annealed gallium oxide thin film to obtain a solar-blind ultraviolet photodetector.
[0008] In some specific embodiments, the strontium titanate substrate is further subjected to cleaning and high-temperature annealing.
[0009] In some specific embodiments, the strontium titanate substrate is (001) oriented.
[0010] In some specific embodiments, in the magnetron sputtering method described in step 1), the background vacuum of magnetron sputtering is ≤1×10⁻⁶. -4 Pa, working gas pressure is 0.4-0.6 Pa, sputtering power is 140-160 W.
[0011] In some specific embodiments, the temperature of the post-annealing treatment in step 2) is 450-550°C, the holding time is 0.5-1.5 hours, and the annealing atmosphere is a mixture of argon and oxygen.
[0012] In some specific embodiments, the gallium oxide thin film is a β-phase polycrystalline thin film with a thickness of 0.8 µm to 1.2 µm.
[0013] In some specific implementations, in step 3), the metal interdigitated electrodes are prepared using electron beam evaporation technology and a metal mask.
[0014] As part of the same inventive concept, this invention provides a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction. The solar-blind ultraviolet photodetector includes a strontium titanate substrate, a single-crystal gallium oxide thin film, and interdigitated electrodes arranged sequentially. The strontium titanate substrate and the gallium oxide thin film form a type I band-aligned heterojunction with a conduction band offset ΔEc of approximately 0.39 eV.
[0015] As part of the same inventive concept, this invention also provides applications of the solar-blind ultraviolet photodetector based on STO-Ga2O3 heterojunction in civilian and military fields.
[0016] Compared with the prior art, the present invention has at least the following advantages: 1) This invention is the first to systematically use STO(001) single crystal substrates for the fabrication of Ga2O3-based solar-blind ultraviolet detectors. By utilizing its excellent lattice matching properties, Ga2O3 films with smoother surfaces (roughness as low as 1.2 nm), higher crystal quality, and lower defect density were obtained. 2) This invention discovers and confirms the formation of a unique type I heterojunction between STO and Ga2O3. This band structure effectively confines photogenerated carriers and greatly suppresses carrier diffusion and recombination, enabling the device to achieve extremely low dark current (2.1 × 10⁻⁶). -12A @1V) and ultra-high photocurrent-to-dark-current ratio (~10) 5 The root cause; 3) The detector prepared in this invention achieves high responsivity (0.23 A / W) and high detectivity (1.93 × 10⁻⁶) at low voltage (5V). 13 With its fast response (48.06 / 9.12 ms), it outperforms similar devices based on traditional sapphire substrates across the board; 4) The preparation method of the present invention has good process compatibility: the preparation process is compatible with mainstream semiconductor processes, has high repeatability, and has the potential for large-scale production. Attached Figure Description
[0017] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.
[0018] Figure 1 The ultraviolet absorption spectrum and band gap calculation diagram of the Ga2O3 thin film of the solar-blind ultraviolet photodetector in Embodiment 2 and Comparative Example 1 of the present invention are shown. Figure 2 The XPS full spectrum of the solar-blind ultraviolet photodetector in Embodiment 2 and Comparative Example 1 of the present invention; Figure 3 The fine Sr 3d spectrum (a) and fine Ti2p spectrum (b) of the STO substrate of the solar-blind ultraviolet photodetector in Embodiment 2 of the present invention are shown. Figure 4 The fine spectra of Ga2O3 in the solar-blind ultraviolet photodetector in Embodiment 2 of the present invention are: O 1s fine spectrum (a) and Ga 3d fine spectrum (b). Figure 5 This is the valence band spectrum of the solar-blind ultraviolet photodetector in Embodiment 2 of the present invention; Figure 6 A schematic diagram of the energy band structure before contact (a) and the schematic diagram of the energy band structure in equilibrium state under illumination for the solar-blind ultraviolet photodetector in Embodiment 2 of the present invention (b); Figure 7 Morphology characterization of the Ga2O3 thin film on the STO substrate of the solar-blind ultraviolet photodetector in Embodiment 2 of the present invention; Figure 8 The rise time and decay time of the solar-blind ultraviolet photodetector in Embodiment 2 of the present invention under 254nm irradiation; Figure 9 The responsivity of the solar-blind ultraviolet photodetector in Embodiment 2 and Comparative Example 1 of the present invention was tested under different light intensities at 254 nm illumination. Figure 10 The normalized detectivity of the solar-blind ultraviolet photodetector in Embodiment 2 and Comparative Example 1 of the present invention is measured under different light intensities at 254 nm illumination. Detailed Implementation
[0019] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are merely descriptive and not limiting, and should not be construed as limiting the scope of protection of the present invention.
[0020] When a quantity, concentration, or other value or parameter is described as a range, preferred range, or preferred upper and lower limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper or preferred values with any lower or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise stated, the numerical range values listed herein include the endpoints of the range and all integers and fractions within that range.
[0021] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.
[0022] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.
[0023] In the following examples and comparative examples, the surface morphology of the prepared films was characterized using atomic force microscopy (AFM, BrukerICON) to obtain their two-dimensional morphology and surface roughness information. Meanwhile, the surface morphology of the annealed Ga2O3 film was observed using field emission scanning electron microscopy (SEM, Thermo Fisher Scientific Apreo 2SHiVac). The crystal structure and phase composition of the thin film were determined by X-ray diffraction (XRD, Malvern Panalytical X'Pert). 3 The powder was analyzed to determine the crystallization state and phase structure changes of the film at 500℃. The chemical composition and elemental valence states of the thin film were determined using X-ray photoelectron spectroscopy (XPS, Thermo Scientific Nexsa G2 Surface Analysis System). The optical absorption properties of the thin film and substrate were measured by ultraviolet-visible absorption spectroscopy (UV–Vis, UV 3103pv) to evaluate their bandgap characteristics and optical absorption edge positions. The optoelectronic performance of the device was tested using a Keithley 2450 source meter; The photoelectric response test uses LEDs of different wavelengths as light sources, and uses an optical power meter to precisely calibrate the optical power density of each light source at the sample location; The switching of the light source is controlled by a function generator to measure the transient optical response characteristics of the device.
[0024] This invention provides a method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction, comprising the following steps: 1) Substrate pretreatment: (001) oriented STO single crystal substrate was selected, and after ultrasonic cleaning with acetone, isopropanol and deionized water, it was dried under high-purity nitrogen and annealed at high temperature in air to obtain an atomically flat surface. 2) Thin film deposition: Ga2O3 thin film was deposited on STO substrate at room temperature in a high vacuum environment using an RF magnetron sputtering system; 3) Post-film annealing: The deposited sample is annealed in an argon-oxygen mixed atmosphere to improve the crystallinity of the film; 4) Electrode fabrication: Gold electrodes were deposited on the surface of Ga2O3 thin films by electron beam evaporation and using interdigitated electrode masks.
[0025] The electron evaporation technology and the metal mask process in the following embodiments are the same, and the specific method steps can be the conventional method steps in the art. Example 1 This embodiment provides a method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction, comprising the following steps: 1) Substrate preparation: (001) oriented STO single crystal substrate (10 mm × 10 mm) was used. It was ultrasonically cleaned in acetone, isopropanol and deionized water for 15 minutes each, and dried with high-purity nitrogen. Then it was annealed in air at 900°C for 1 hour in a tube furnace. 2) Thin film deposition: The pretreated STO substrate is placed into a magnetron sputtering system, wherein the base vacuum of the magnetron system is evacuated to 1×10⁻⁶. -5 High-purity argon gas was introduced at 0.4 Pa, and the working pressure was maintained at 0.4 Pa. The radio frequency power was set to 160 W, and sputtering was performed at room temperature for 90 minutes to obtain a Ga2O3 film with a thickness of 1.2 µm. 3) Post-annealing: The sample obtained in step 3) is annealed in a tube furnace in a flowing argon / oxygen mixed atmosphere (flow rate ratio 100:3 sccm), while the temperature is increased to 450℃ at a rate of 2℃ / min and held for 1.5 hours. 4) Electrode preparation: Using electron beam evaporation technology, a 50 nm thick interdigitated gold electrode was deposited on the surface of the Ga2O3 thin film using a metal mask (using a small gold plating instrument, gold target material was plated for 120 s) to obtain a solar-blind ultraviolet photodetector.
[0026] Example 2 This embodiment provides a method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction, comprising the following steps: 1) Substrate preparation: (001) oriented STO single crystal substrate (10 mm × 10 mm) was used. It was ultrasonically cleaned in acetone, isopropanol and deionized water for 15 minutes each, and dried with high-purity nitrogen. Then it was annealed in air at 900°C for 1 hour in a tube furnace. 2) Thin film deposition: The pretreated STO substrate is placed into a magnetron sputtering system, wherein the base vacuum of the magnetron system is evacuated to 1×10⁻⁶. -4 Pa, high-purity argon gas was introduced, and the working pressure was maintained at 0.5 Pa; the radio frequency power was set to 150 W, and sputtering was performed at room temperature for 90 minutes to obtain a Ga2O3 film with a thickness of 1 µm; 3) Post-annealing: The sample obtained in step 3) is annealed in a tube furnace in a flowing argon / oxygen mixed atmosphere (flow rate ratio 100:3 sccm), while the temperature is increased to 500℃ at a rate of 2℃ / min and held for 1 hour. 4) Electrode preparation: Using electron beam evaporation technology, a 50 nm thick interdigitated gold electrode was deposited on the surface of the Ga2O3 thin film using a metal mask (using a small gold plating instrument, gold target material was plated for 120 s) to obtain a solar-blind ultraviolet photodetector.
[0027] Example 3 This embodiment provides a method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction, comprising the following steps: 1) Substrate preparation: (001) oriented STO single crystal substrate (10 mm × 10 mm) was used. It was ultrasonically cleaned in acetone, isopropanol and deionized water for 15 minutes each, and dried with high-purity nitrogen. Then it was annealed in air at 850°C for 1.5 hours in a tube furnace. 2) Thin film deposition: The pretreated STO substrate is placed into a magnetron sputtering system, wherein the base vacuum of the magnetron system is evacuated to 1×10⁻⁶. -5 High-purity argon gas was introduced at 0.6 Pa, and the working pressure was maintained at 0.6 Pa. The radio frequency power was set to 140 W, and sputtering was performed at room temperature for 90 minutes to obtain a Ga2O3 film with a thickness of 0.8 µm. 3) Post-annealing: The sample obtained in step 3) is annealed in a tube furnace in a flowing argon / oxygen mixed atmosphere (flow rate ratio 100:3 sccm), while the temperature is increased to 550℃ at a rate of 2℃ / min and held for 0.5 hours. 4) Electrode preparation: Using electron beam evaporation technology, a 50 nm thick interdigitated gold electrode was deposited on the surface of the Ga2O3 thin film using a metal mask (using a small gold plating instrument, gold target material was plated for 120 s) to obtain a solar-blind ultraviolet photodetector.
[0028] Comparative Example 1 This embodiment provides a method for fabricating a solar-blind ultraviolet photodetector based on sapphire-Ga2O3, including the following steps: 1) Substrate preparation: A sapphire (Al2O3) substrate (10 mm × 10 mm) was used. It was ultrasonically cleaned in acetone, isopropanol and deionized water for 15 minutes each, and then dried with high-purity nitrogen. It was then annealed in air at 900°C for 1 hour in a tube furnace. 2) Thin film deposition: The pretreated sapphire substrate is placed in a magnetron sputtering system, wherein the base vacuum of the magnetron system is evacuated to 1×10⁻⁶. -4 Pa, high-purity argon gas was introduced, and the working pressure was maintained at 0.5 Pa; the radio frequency power was set to 150 W, and sputtering was performed at room temperature for 90 minutes to obtain a Ga2O3 film with a thickness of 1 µm; 3) Post-annealing: The sample obtained in step 3) is annealed in a tube furnace in a flowing argon / oxygen mixed atmosphere (flow rate ratio 100:3 sccm), while the temperature is increased to 500℃ at a rate of 2℃ / min and held for 1 hour. 4) Electrode preparation: Using electron beam evaporation technology, a 50 nm thick interdigitated gold electrode was deposited on the surface of the Ga2O3 thin film using a metal mask (using a small gold plating instrument, gold target material was plated for 120 s) to obtain a solar-blind ultraviolet photodetector.
[0029] Product characterization and performance testing This application uses Example 2 as an example to characterize and test the solar-blind ultraviolet photodetectors prepared in Example 2 and Comparative Example 1, specifically as follows: 1) Ultraviolet light test This application tests the optical properties of the thin films in the solar-blind ultraviolet photodetectors prepared in Example 2 and Comparative Example 1, and the results are as follows: Figure 1 As shown, films grown on both STO and sapphire (Al₂O₃) substrates exhibit strong absorption in the solar-blind ultraviolet band. Using Tauc plot extrapolation, the optical bandgap of the Ga₂O₃ film on the STO substrate was calculated to be approximately 3.16 eV, while the bandgap of the Ga₂O₃ film grown on the sapphire substrate was approximately 4.48 eV. This significant difference indicates that substrate properties profoundly influence the chemical composition and crystal structure of the ultimately formed functional layer.
[0030] 2) X-ray photoelectron spectroscopy test This application analyzes the surface chemical state and band structure of the thin films in the solar-blind ultraviolet photodetectors prepared in Example 2 and Comparative Example 1, and the results are as follows: Figure 2 XPS full spectra of gallium oxide thin films grown on sapphire and STO substrates are shown. As can be seen from the figure, the XPS measurement spectrum of the gallium oxide thin film grown on sapphire clearly shows the characteristic peaks of Ga and O, proving that the main component of the film is gallium oxide, and no obvious impurity element peaks were detected, indicating the high purity of the film. The XPS measurement spectrum of the gallium oxide thin film grown on the STO substrate clearly shows the characteristic peaks of Ti, Sr and O, and no obvious impurity element peaks were detected, indicating the high purity of the STO substrate.
[0031] 3) Fine elemental spectral analysis: This application performed fine elemental spectral analysis on the STO substrate in the solar-blind ultraviolet photodetector prepared in Example 2.
[0032] The results are as follows Figure 3 Images a and 3b show the fine spectra of Sr 3d and Ti 2p on the STO substrate, respectively. The Sr 3d spectrum exhibits a typical double-peak structure, with the peaks located at 134.41 eV and 132.65 eV, respectively. The Ti 2p fine spectrum shows clear double peaks of Ti2p3 / 2 and Ti2p1 / 2 spin orbitals, located at 458.17 eV and 463.84 eV, respectively, indicating that Ti is distributed as Ti2p3 / 2 and Ti2p1 / 2 spin orbitals. 4+ The state exists; simultaneously, the chemical state of the gallium oxide thin film in the solar-blind ultraviolet photodetector prepared in Example 2 was analyzed, and the results are as follows. Figure 4 The O 1s spectrum shown in a can be deconvolved into two components: the main peak at 530.79 eV corresponds to lattice oxygen (Ga-O), while the higher binding energy component at 532.2 eV is usually attributed to surface-adsorbed oxygen or hydroxyl species. Figure 4 The Ga 3d spectrum shown in b can be fitted by a single peak, and its binding energy is located at 20.7 eV, which is attributed to Ga. 3+ With O 2- The chemical bonds between them (Ga-O bonds) are a typical characteristic of β-Ga2O3. These results collectively confirm that this application successfully prepared Ga2O3 thin films with ideal stoichiometry.
[0033] 4) XPS valence band spectrum test To understand the underlying carrier transport mechanism of the device, XPS valence band spectroscopy in this application determined the valence band apex position of the solar-blind ultraviolet photodetector prepared in Example 2. The results are as follows: Figure 5As shown, the valence band spectrum of the STO substrate shows that its VBM is at 2.10 eV, while the VBM of Ga2O3 formed on the STO substrate is at 3.03 eV. This significant valence band shift (~0.93 eV) is a typical characteristic of band alignment at the heterojunction interface.
[0034] Based on the Kraut method (Equations (4) and (5)), this application quantitatively calculated the band shift between STO and Ga2O3: (4) (5) Given that the band gap of STO is 3.16 eV and the band gap of Ga2O3 is 4.48 eV, we can calculate ∇Ec = 0.39 eV by substituting the values into formulas (4) and (5).
[0035] Based on the above calculation results, this application presents a schematic diagram of the band alignment of the STO / Ga2O3 heterojunction. Specifically, the band structure before contact is shown below. Figure 6 (Left) shows the intrinsic energy level positions of the two materials when they are not in contact. After contact and reaching thermal equilibrium, band bending occurs at the interface due to Fermi level alignment, forming a structure like... Figure 6 The band structure shown on the right clearly reveals a typical type I heterojunction structure; this unique type I band structure of the photodetector has efficient carrier confinement and extremely low dark current.
[0036] In the type I bandgap arrangement, the conduction band bottom and valence band top of STO are completely enveloped by the wider band structure of Ga2O3. This structure effectively confines photogenerated electrons and holes within the STO active layer, significantly reducing carrier diffusion to the electrodes and recombination losses at the interface; while the extremely high conduction and valence band barriers act as a barrier, preventing carrier escape under low bias voltage, thus achieving an extremely low dark current (2.1 × 10⁻⁶). -12 A); This is precisely why the device can achieve an ultra-high light-to-dark current ratio (1.57 × 10⁻⁶). 5 The fundamental physical reason for this.
[0037] Unlike simple Ga2O3 thin film devices fabricated on insulating sapphire substrates, this application uses STO / Ga2O3 to form a functional heterojunction. The STO substrate itself, as a wide bandgap semiconductor, actively participates in the generation, separation, and transport of charge carriers through its band structure coupling with Ga2O3, rather than simply acting as a passive supporting substrate. The built-in electric field generated by this junction effect provides additional driving force for photogenerated charge carriers, thereby improving the collection efficiency of charge carriers and contributing to a higher device responsivity (0.23 A / W).
[0038] 5) Morphological characteristics In this application, the solar-blind ultraviolet photodetector prepared in Example 2 was characterized in terms of its morphology. The surface SEM morphology image and cross-sectional SEM morphology image are shown below. Figure 7 As shown in Figures a and 7b, the thickness of the Ga2O3 film formed on the STO substrate is 992 nm, as can be seen from the cross-sectional morphology diagram.
[0039] To quantitatively compare the surface smoothness of the thin films, this application underwent atomic force microscopy (AFM) analysis. Figure 7 Images c and 7d show the two-dimensional AFM topography (scan range: 5 μm × 5 μm) of gallium oxide films grown on STO and sapphire substrates, respectively. Analysis results show that the Ga₂O₃ film on STO exhibits lower surface roughness, with a root mean square roughness of only 1.2 nm; in contrast, the film of the same thickness grown on the sapphire substrate shows a higher roughness (3.2 nm). This significant difference is visually reflected in the topography images: the film on STO ( Figure 7 c) The surface is smoother and more uniform, with regular grain arrangement; while the thin film on sapphire ( Figure 7 d) The surface exhibits greater undulations and a relatively wider grain size distribution, with more pronounced protrusions and peaks / valleys. This superior morphology can be attributed to the smaller lattice mismatch between the STO substrate and Ga2O3, which promotes two-dimensional layered growth of the film with a lower nucleation barrier and epitaxial strain, resulting in Ga2O3 films with higher crystallinity and lower defect density. The microstructure and surface morphology of the film have a decisive influence on its photoelectric properties. responsiveness This application measured the rise time and decay time of the photodetector under 254 nm illumination, and the results are as follows: Figure 8 As shown in the figure, the rise time and decay time of the solar-blind ultraviolet photodetector provided in this application under 254 nm irradiation are 48.06 ms and 9.12 ms, respectively. The faster response speed, especially the faster decay process, is mainly due to the high crystal quality and low defect density of the Ga2O3 film grown on the STO substrate.
[0040] The sensitivity of a photodetector is usually measured by its responsivity (R), which is calculated as follows: Where Ip is the photocurrent, Id is the dark current, P is the incident light power density, and S is the effective illumination area of the device. Figure 9The responsivity of STO-Ga2O3 photodetectors and Ga2O3 photodetectors (specifically referring to sapphire / Ga2O3 photodetectors, hereinafter the same) under different light intensities at 254 nm illumination is compared. The results show that the responsivity of STO-Ga2O3 photodetectors is always higher than that of Ga2O3 photodetectors, with the former reaching 0.23 A / W and the latter only 0.0245 A / W. This is directly attributed to the higher photocurrent collection efficiency and lower dark current of STO-based devices. The root cause lies in the high-quality thin film microstructure induced by STO, which promotes the efficient generation and transport of photogenerated carriers while minimizing non-radiative recombination losses.
[0041] Normalized detectivity (D*) measures the ability of a photodetector to detect weak light and is an important parameter for evaluating its performance. The calculation formula is as follows: Where R is the responsivity, S is the effective illumination area of ultraviolet light, and q is the charge per unit charge (1.6 × 10⁻⁶). - 19 C), I d It is the dark current of the device, among which Figure 10 The normalized detectivity of STO-Ga2O3 photodetectors and Ga2O3 photodetectors under different light intensities at 254 nm illumination was compared. The results show that the normalized detectivity of the STO-Ga2O3 photodetector is much higher than that of the Ga2O3 photodetector, reaching as high as 1.93 × 10⁻⁶. 13 Jones, the latter is only 1.47×10 11 Jones's is two orders of magnitude higher, with extremely low dark current. The amplification effect of increasing D* by the inverse of the square root is the decisive factor in obtaining ultra-high detection rate.
[0042] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.
Claims
1. A method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction, characterized in that, Includes the following steps: 1) Gallium oxide thin films were deposited on strontium titanate substrates using magnetron sputtering; 2) The deposited gallium oxide film is post-annealed in an inert atmosphere; Metal interdigitated electrodes were fabricated on the surface of the annealed gallium oxide thin film to obtain a solar-blind ultraviolet photodetector.
2. The method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction according to claim 1, characterized in that, It also includes cleaning and high-temperature annealing of the strontium titanate substrate.
3. The method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction according to claim 2, characterized in that, The strontium titanate substrate is (001) oriented.
4. The method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction according to claim 3, characterized in that, In the magnetron sputtering method described in step 1), the background vacuum of magnetron sputtering is ≤1×10⁻⁶. -4 Pa, working gas pressure is 0.4-0.6 Pa, sputtering power is 140-160 W.
5. The method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction according to claim 1, characterized in that, The post-annealing treatment in step 2) is performed at a temperature of 450-550℃, with a holding time of 0.5-1.5 hours, and the annealing atmosphere is a mixture of argon and oxygen.
6. The method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction according to claim 5, characterized in that, The gallium oxide thin film is a β-phase polycrystalline thin film with a thickness of 0.8 µm to 1.2 µm.
7. The method for fabricating a solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction according to claim 1, characterized in that, In step 3), the metal interdigitated electrodes are prepared using electron beam evaporation technology and a metal mask.
8. A solar-blind ultraviolet photodetector based on an STO-Ga2O3 heterojunction prepared by the preparation method according to claims 1-7, characterized in that, The solar-blind ultraviolet photodetector includes an STO substrate, a single-crystal gallium oxide thin film, and interdigitated electrodes arranged sequentially; wherein the strontium titanate substrate and the gallium oxide thin film form a type I band-aligned heterojunction with a conduction band offset ΔEc of approximately 0.39 eV.
9. An application of the solar-blind ultraviolet photodetector based on STO-Ga2O3 heterojunction as described in claim 8 in civilian and military fields.