A Si-doped lithium gallate thin film solar blind ultraviolet detector, a preparation method and application thereof

Abstract

This invention provides a Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector, its fabrication method, and its application. The fabrication method includes the following steps: mixing SiO2, Li2CO3, and Ga2O3 polycrystalline powders, and using a solid-state reaction method to obtain Li... y (Ga 1‑x Si x 5O8 polycrystalline target material; Li was prepared on the substrate using pulsed laser deposition. y (Ga 1‑x Si x )5O8 thin film; subsequently in Li y (Ga 1‑x Si x Electrode deposition on 5O8 thin film. Compared with undoped Si Li 0.9 Compared with Ga5O8 thin-film detectors, the solar-blind ultraviolet detector provided by this invention has improved the on / off ratio, responsivity, and detectivity by up to 1177 times, 1130 times, and 1153 times, respectively, and shortened the response time by up to 0.5 s. It has stable working performance and can be applied to fields involving solar-blind ultraviolet signal detection, such as forest fire monitoring and missile exhaust tracking.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, specifically relating to a Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector, its preparation method, and its application. Background Technology

[0002] Ultraviolet (UV) radiation is a crucial component of the electromagnetic spectrum. Wavelengths shorter than 280 nm are completely absorbed by the ozone layer, making it virtually impossible for UV radiation to reach the Earth's surface; this band is known as the solar-blind UV region. Compared to infrared and visible light, utilizing the solar-blind UV band for detection effectively avoids interference from solar radiation, significantly improving the signal-to-noise ratio and sensitivity of the detection system. Therefore, it possesses irreplaceable strategic and application value in numerous high-tech fields, including military early warning, space communication, flame monitoring, environmental monitoring (such as ozone layer change and pollutant gas detection), biomedicine, and industrial process control.

[0003] In the field of solar-blind ultraviolet detection, early photomultiplier tubes required high voltage operation, resulting in large size and weight; while silicon-based detectors required additional filters, which increased system complexity. Therefore, semiconductor materials with intrinsically wide bandgap (>4.5 eV) (such as MgZnO, AlGaN, gallium oxide, and diamond) have become ideal choices for fabricating solar-blind ultraviolet detectors. However, ternary compounds such as AlGaN and MgZnO still face significant challenges: AlGaN requires the introduction of high-concentration aluminum components to widen the bandgap, but high aluminum doping degrades the crystal quality of the material, thus limiting device performance; when the magnesium content exceeds a certain threshold, MgZnO is prone to ZnO / MgO phase separation, leading to dislocation and defect proliferation and significant degradation of photoelectric properties.

[0004] In contrast, the thermodynamically stable phase of gallium oxide—β-Ga₂O₃—is an emerging ultra-wide bandgap semiconductor material with an intrinsic bandgap of approximately 4.9 eV (corresponding to a wavelength of 253 nm), making it highly suitable for solar-blind ultraviolet detection. However, detectors based on pure β-Ga₂O₃ still have significant room for improvement in terms of response speed, dark current, and carrier transport efficiency. Furthermore, p-type doping remains a global challenge, limiting the development of Ga₂O₃-based PN or PIN junction devices and thus hindering the further development of this material in the field of photodetectors. Therefore, exploring novel high-sensitivity solar-blind ultraviolet detection materials is of great significance.

[0005] LiGa5O8, with its spinel structure, is a potential ultrawide-bandgap oxide semiconductor material with a bandgap as high as 5.36 eV, corresponding to a wavelength of approximately 233 nm. Compared to gallium oxide (β-Ga2O3), which has a bandgap of 4.9 eV (corresponding to 253 nm), the wider bandgap theoretically allows LiGa5O8-based detectors to exhibit a sensitive response to shorter wavelengths of deep ultraviolet light (especially around 233 nm). This characteristic gives it a unique advantage in the field of solar-blind ultraviolet detection, enabling it to detect shorter wavelengths of ultraviolet light that gallium oxide detectors cannot effectively respond to. However, the intrinsic LiGa5O8 thin film detectors reported so far generally suffer from problems such as low photocurrent and slow response speed (Hao Zhao, Bo-Wen Yu, Qi Li, et al. Growth of LiGa5O8 SingleCrystal Thin Films and Their Conductive Mechanism by the Mist-CVD Method, Journal of synthetic crystals 54, 998-1004 (2025).), which limits their practical application. Therefore, it is particularly urgent to further improve their performance. Summary of the Invention

[0006] To address the aforementioned technical problems, the primary objective of this invention is to provide a Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector.

[0007] Another object of the present invention is to provide a method for fabricating the above-mentioned Si-doped lithium gallate thin film solar-blind ultraviolet detector.

[0008] Another object of the present invention is to provide the application of the above-mentioned Si-doped lithium gallate thin film solar-blind ultraviolet detector.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector, comprising, from bottom to top, a substrate layer, a Li... y (Ga 1- x Si x )5O8 thin film layer and metal electrode layer, wherein 0.01≤x≤0.07, 0.9≤y≤1.1.

[0011] Preferably, the values ​​of x and y are 0.07 and 0.9, respectively.

[0012] Preferably, the substrate is a MgAl2O4 substrate and the metal electrode layer is a gold electrode.

[0013] More preferably, the MgAl2O4 substrate is a single crystal of MgAl2O4 polished on one or both sides, with a size of 5-10 mm × 5-10 mm and a thickness of 0.2-1 mm.

[0014] More preferably, the gold electrode is an interdigitated gold electrode, wherein the finger width in the interdigitated electrode pattern is 100-500 μm, the finger spacing is 100-500 μm, and the finger length is 1.5-3 mm.

[0015] This invention provides a method for fabricating a Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector, comprising the following steps:

[0016] Step 1. Mix SiO2, Li2CO3 and Ga2O3 raw material powders, and calcine them at 1200-1350℃ for 6-8 hours using a solid-state reaction method to obtain Li. y (Ga 1-x Si x 5O8 polycrystalline sputtering target, where x ranges from 0.01 to 0.07 and y ranges from 0.9 to 1.1;

[0017] Step 2. Using pulsed laser deposition in an oxygen atmosphere, Li y (Ga 1-x Si x )5O8 polycrystalline target material, Li is grown on the substrate y (Ga 1-x Si x )5O8 thin film, wherein 0.01≤x≤0.07, 0.9≤y≤1.1, the film growth temperature is 550-650℃, and the oxygen partial pressure is 2.5-10 Pa;

[0018] Step 3. Using a miniature ion sputtering instrument and a custom-made mask on the Li y (Ga 1-x Si x Metal electrodes were deposited on 5O8 thin films to construct a photodetector with a metal-semiconductor-metal (MSM) planar electrode structure.

[0019] Preferably, in step 1, the solid-state reaction method specifically includes:

[0020] S1, based on the chemical formula Li y (Ga 1-x Si x The amounts of SiO2, Li2CO3 and Ga2O3 polycrystalline powders are determined by x, which is 0.01-0.07 and y is 0.9-1.1.

[0021] S2. Place the SiO2, Li2CO3 and Ga2O3 polycrystalline powders weighed in step S1 into a ball mill jar, add anhydrous ethanol, and mix by ball milling.

[0022] S3. Dry the powder that was uniformly mixed by ball milling in step S2, and pre-calcine it at 900-1000℃ in air atmosphere. After pre-calcinement, cool it to room temperature with the furnace, then grind the powder and sieve it to obtain Li. y (Ga 1-x Si x )5O8 powder;

[0023] S4. The Li obtained in step S3 y (Ga 1-x Si x The 5O8 powder sample was placed in a ball mill jar, anhydrous ethanol was added, and it was ball milled a second time.

[0024] S5. Mix the powder sample obtained in step S4 with a small amount of polyvinyl alcohol aqueous solution, grind it thoroughly and then sieve it. Pour the sieved powder into an isostatic pressing mold and press it into a target blank.

[0025] S6. Place the pressed target blank into a muffle furnace, first heat to 600℃, and remove the organic binder at 600℃ for 2 hours. Then heat to 1200-1350℃ and sinter for 6-8 hours. After furnace cooling, the Li is obtained. y (Ga 1-x Si x 5O8 target material.

[0026] More preferably, the ball milling described in steps S2 and S4 is carried out in a planetary ball mill with a rotation speed of 200-500 r / min and a milling time of 5-12 hours.

[0027] The heating rate for preheating in step S3 is 4-10 °C / min;

[0028] The polyvinyl alcohol aqueous solution in step S5 has a mass fraction of 3-8%, and the pressing pressure is 100-250 MPa;

[0029] The heating rate for sintering in step S6 is 2-8 °C / min;

[0030] The sieving mentioned in steps S3 and S5 refers to sieving through a 120-mesh sieve.

[0031] Preferably, in step 2, the pulsed laser energy density of the pulsed laser deposition method is 0.9-1.5 J / cm². 2 The pulsed laser frequency is 5-10 Hz, the number of pulses is 900-9000, the substrate temperature is 550-650℃, and the oxygen partial pressure is 2.5-10 Pa.

[0032] Preferably, in step 2, the pulsed laser deposition method specifically includes:

[0033] (1) The substrate is fixed to the heating plate with silver paste, and the Li y (Ga 1-x Si x The 5O8 target material is attached to the stainless steel target holder. The heating holder and the target material are placed together in the vacuum cavity of the pulsed laser deposition system, and the distance between the substrate and the target material is set to 4-5 cm.

[0034] (2) Use a dry pump to evacuate the gas pressure inside the cavity to below 10 Pa, and then use a molecular pump to evacuate the vacuum to 10 Pa. -4 Below Pa;

[0035] (3) Turn on the laser heater to heat the substrate to 550-650℃ and maintain the temperature constant;

[0036] (4) Close the slide valve, turn on the gas flow controller to introduce oxygen into the cavity, and use the side valve to fine adjust the gas pressure in the cavity to maintain the background oxygen partial pressure in the cavity at 2.5-10 Pa.

[0037] (5) Use a baffle to block the heating support, and set the ceramic target to move along the x-axis and y-axis at a speed of 0.01-0.3 mm / s. Set the pulsed laser energy density to 0.9-1.5 J / cm². 2 The pulsed laser frequency is 5-10 Hz, the number of pulses is 900-9000, the laser is turned on, and the target material is pre-sputtered for 3-10 minutes to remove surface contaminants.

[0038] (6) After the pre-sputtering is completed, the heating holder is set to rotate at a speed of 3-10 rpm, and then the baffle is removed to start the epitaxial growth of the thin film on the substrate;

[0039] (7) After deposition, maintain the background oxygen partial pressure at 2.5-10 Pa and cool down at a rate of 10-50 ℃ / min;

[0040] (8) Lower the temperature inside the cavity to below 200°C, turn off the molecular pump and the dry pump, introduce nitrogen into the vacuum cavity to bring the pressure inside the cavity back to atmospheric pressure, remove the heating holder, and obtain the Li. y (Ga 1-x Si x )5O8 film.

[0041] More preferably, the heating rate in step (3) is 10-50 °C / min.

[0042] Preferably, in step 3, the metal electrode is a gold electrode, and when using a small ion sputtering instrument, the cavity pressure is set to 6-12 Pa, the current to 6-12 mA, and the time to 120-240 s.

[0043] The Si-doped Li of the present invention y (Ga 1-x Si x The 5O8 thin-film solar-blind ultraviolet detector can be applied to fields involving the detection of solar-blind ultraviolet signals, such as forest fire monitoring and missile exhaust plume tracking. Its working principle is as follows:

[0044] When a certain bias voltage is applied across the interdigitated electrodes, in a dark environment, there are no photogenerated carriers inside the detector, resulting in extremely high intrinsic resistance and suppressing the dark current to an extremely low level (only on the order of pA at a 10 V bias voltage). Under solar-blind ultraviolet light (such as 254 nm) irradiation, the interdigital gap between the electrodes acts as a Li y (Ga 1-x Si x In the active layer of 5O8 that receives light, valence band electrons absorb photon energy and transition to the conduction band, simultaneously generating conductive holes in the valence band. This process generates a large number of electron-hole pairs, causing a sharp increase in carrier concentration. Under an applied bias voltage, these electrons and holes drift towards the two ends of the electrode and are collected by the gold electrode, resulting in a circuit current increase of several orders of magnitude compared to the dark state (reaching the μA level at 10 V), while the resistance drops sharply accordingly. This photoelectric signal is detected by an external circuit, thus achieving highly sensitive detection of solar-blind ultraviolet light.

[0045] The beneficial effects of this invention are as follows:

[0046] 1. The thin film obtained by the present invention has excellent crystallinity and surface smoothness, which is beneficial for the continued growth of other high-quality thin films and superlattice structures on the upper layer of the thin film.

[0047] 2. The photodetector fabricated in this invention exhibits characteristics such as low dark current, high on / off ratio, high detectivity, and fast response speed. Compared with intrinsic LiGa5O8 thin-film detectors reported in existing literature, the Si-doped LiGa5O8 thin-film photodetector provided in this invention shows a maximum improvement of 1177 times in on / off ratio, a maximum improvement of 1130 times in responsivity, a maximum improvement of 1153 times in detectivity, and a maximum improvement of 0.5 s in response time, indicating a significant enhancement in the overall detection performance of the device.

[0048] 3. The Li obtained by this invention y (Ga 1-x Si xThe 5O8 thin-film solar-blind ultraviolet detector has good wavelength selectivity and stability in the deep ultraviolet band with wavelengths less than 260 nm, and can be applied to fields that require the detection of solar-blind ultraviolet signals, such as forest fire monitoring and missile exhaust tracking.

[0049] 4. The photocurrent I of the solar-blind ultraviolet detector prepared by this invention has a linear relationship with the optical power P. The fitting exponent n is 1.007, and it also has good application prospects in the field of optical power meters.

[0050] 5. In the preparation method of the present invention, the material used for growing Li y (Ga 1-x Si x The target material for the 5O8 thin film was a self-synthesized Si-doped Li. y (Ga 1-x Si x 5O8 polycrystalline target material. The pulsed laser deposition technology used can precisely control the chemical composition and lattice orientation of the thin film, thereby achieving high-quality thin film growth with the expected stoichiometry.

[0051] 6. The photodetector fabricated in this invention is a metal-semiconductor-metal planar structure. This structure features relatively simple fabrication process, high light conversion efficiency, low dark current, high photoresponsivity, and fast response speed. It is also easy to integrate and shows promising application prospects in the field of solar-blind ultraviolet detection. Attached Figure Description

[0052] Figure 1 This is a simplified structural diagram of the Si-doped lithium gallate thin film solar-blind ultraviolet detector prepared in Examples 1-5 of the present invention.

[0053] Figure 2 Li prepared with SiO2 gradient doping concentration (x) in Examples 1-5 0.9 (Ga 1-x Si x The XRD pattern of the 5O8 thin film and the magnified image of the diffraction peaks corresponding to the (400) crystal plane of the thin film are shown. x=0%, x=1%, x=3%, x=5%, and x=7% represent the Li₂ prepared in Examples 2, 3, 4, 5, and 1, respectively. 0.9 (Ga 1-x Si x )5O8 film.

[0054] Figure 3 Li prepared in Example 1 0.9 (Ga 0.93 Si 0.07 Atomic force microscopy image of a 5O8 thin film sample.

[0055] Figure 4 Li prepared in Example 1 0.9 (Ga 0.93 Si 0.07 Cross-sectional scanning electron microscope image of the 5O8 thin film sample.

[0056] Figure 5 Li prepared with SiO2 gradient doping concentration (x) in Examples 1-5 0.9 (Ga 1-x Si x The UV-Vis transmission spectra of the SiO2 thin films are shown in the inset. The inset shows the LiO2 films prepared in Examples 1-5 with varying SiO2 doping concentrations (x). 0.9 (Ga 1-x Si x (αhν) of 5O8 thin film 2 -(hν) linear fitting plot, where x=0%, x=1%, x=3%, x=5%, and x=7% represent the Li prepared in Examples 2, 3, 4, 5, and 1, respectively. 0.9 (Ga 1-x Si x )5O8 film.

[0057] Figure 6 Li prepared with SiO2 gradient doping concentration (x) in Examples 1-5 0.9 (Ga 1-x Si x The current-voltage (IV) characteristic curve of the 5O8 thin-film photodetector is shown in the figure, where x=0%, x=1%, x=3%, x=5%, and x=7% represent the Li₂ prepared in Examples 2, 3, 4, 5, and 1, respectively. 0.9 (Ga 1-x Si x )5O8 film.

[0058] Figure 7 Li prepared in Example 1 0.9 (Ga 0.93 Si 0.07 )5O8 thin-film photodetector and Li prepared in Example 2 0.9 Current-time (IT) characteristic curves and their fitting curves of Ga5O8 thin-film photodetectors.

[0059] Figure 8 Li prepared in Example 1 0.9 (Ga 0.93 Si 0.07 The curves of photocurrent and incident light power density of a 5O8 thin-film photodetector under a bias voltage of 10 V and their fitting curves.

[0060] Figure 9 Li prepared in Example 1 0.9 (Ga 0.93 Si 0.07 )5O8 thin-film photodetector and Li prepared in Example 2 0.9 The responsivity of a Ga5O8 thin-film photodetector varies with incident light power density. Detailed Implementation

[0061] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0062] All raw materials involved in this invention can be purchased directly from the market. For process parameters not specifically specified, conventional techniques can be used as a reference.

[0063] Example 1

[0064] The specific fabrication method of the Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector in this embodiment includes the following steps:

[0065] Step 1: Weigh 0.5258 g of SiO2 powder, 0.8313 g of Li2CO3 powder, and 10.8954 g of Ga2O3 powder. Place the weighed powder raw materials into an agate ball mill jar, add anhydrous ethanol, and ball mill to mix. After the powder is evenly mixed, dry it and place it in a muffle furnace for pre-calcination. The pre-calcination includes heating the sample to 900℃ at a heating rate of 4℃ / min, holding it at that temperature for 8 hours, and then cooling it with the furnace.

[0066] Step Two: Place the powder sample obtained in Step One in an agate ball mill jar, add anhydrous ethanol for a second ball milling, dry the uniformly mixed powder, mix with a small amount of polyvinyl alcohol aqueous solution, grind thoroughly, and sieve. Pour the sieved powder into an isostatic pressing mold and press it into a circular solid with a diameter of 28 mm. Place the pressed target blank in a muffle furnace for sintering, and after cooling, obtain the Li. 0.9 (Ga 0.93 Si 0.07 5O8 target material; the pressure is 194 MPa, and the sintering includes: heating to 600°C at a heating rate of 4°C / min, removing the binder at 600°C for 2 hours, heating to 1260°C at a heating rate of 4°C / min, sintering at high temperature for 6 hours, and then cooling with the furnace.

[0067] Step 3: Fix a 5 mm × 5 mm double-sided polished MgAl2O4 single crystal substrate onto the heating holder with silver paste, bake at 100℃ for 10 min, and after the silver paste is completely dry, put the heating holder and the target material into the vacuum cavity of the pulsed laser deposition system together, and set the distance between the substrate and the target material to 5 cm.

[0068] Step 4: First, use a dry pump to evacuate the gas pressure inside the chamber to below 10 Pa, then use a molecular pump to evacuate the vacuum to 10 Pa. -4 Below Pa, turn on the laser heater to heat the substrate to 600°C and maintain the temperature constant, close the gate valve, turn on the gas flow controller to introduce high-purity oxygen into the cavity, and use the bypass valve to fine-tune the gas pressure in the cavity to maintain the background oxygen partial pressure in the cavity at 7.5 Pa; the heating rate is 30 °C / min.

[0069] Step 5: Block the heating support with a baffle, and set the ceramic target to move along the x-axis and y-axis at a speed of 0.1 mm / s. Set the pulsed laser energy density to 1.1 J / cm². 2 The frequency of the pulsed laser is 5 Hz and the number of pulses is 3600. The laser is turned on and the target is pre-sputtered for 5 minutes to remove surface contaminants. After the pre-sputtering is completed, the baffle is removed and the heating holder is set to rotate at a speed of 5 rpm. Thin film epitaxial growth is started on the MgAl2O4 substrate.

[0070] Step Six: After deposition, maintain the background oxygen partial pressure at 7.5 Pa and cool at a rate of 30 °C / min. When the cavity temperature drops below 200 °C, turn off the molecular pump and dry pump, and introduce nitrogen gas into the vacuum chamber to restore the cavity pressure to atmospheric pressure. Remove the heated tray to obtain Li with a thickness of approximately 148 nm. 0.9 (Ga 0.93 Si 0.07 )5O8 film;

[0071] Step 7: Take the Li obtained in Step 6 0.9 (Ga 0.93 Si 0.07 The 5O8 thin film was placed in a small ion sputtering instrument, the cavity vacuum was set to 9 Pa, the current was 9 mA, and the sputtering time was 180 s. Interdigitated gold electrodes were deposited on the thin film using a custom mask. The interdigitated electrode pattern had a finger width of 500 μm, a finger spacing of 500 μm, and a finger length of 2.25 mm, thus constructing an MSM-type photodetector.

[0072] Examples 2-5

[0073] Examples 2-5 show the preparation of Li following the steps outlined in Example 1. y (Ga 1-x Six The 5O8 thin film differs from that in Example 1 in the molar ratio of SiO2 and Ga2O3, as detailed in Table 1.

[0074] Table 1

[0075]

[0076] The Li obtained through the above embodiments and comparative examples 0.9 (Ga 1-x Si x Characterization data of the 5O8 thin film sample are as follows: Figures 2-9 As shown. Figure 1 The simplified structural schematic diagrams of the Si-doped lithium gallium oxide thin-film solar-blind ultraviolet photodetector embodiments and comparative examples of the present invention are provided, including a MgAl2O4 substrate and Li2O4 grown on the MgAl2O4 substrate. 0.9 (Ga 1-x Si x )5O8 thin film and set in Li 0.9 (Ga 1-x Si x Electrode on 5O8 thin film.

[0077] Figure 2 The SiO2 gradient doped Li is given 0.9 (Ga 1-x Si x The XRD pattern of the LiGa5O8 thin film and the magnified view of the diffraction peaks corresponding to the (400) crystal plane are shown in the figure. It can be seen from the figure that there are two diffraction peaks near 2θ = 43.22° and 94.95°, but these deviate from the angles corresponding to the (400) and (800) crystal planes of the cubic LiGa5O8 (PDF# 38-1371). This may be because the cell parameter of LiGa5O8 is 8.203 Å, while the cell parameter of the substrate MgAl2O4 is 8.083 Å. The large lattice mismatch between the film and the substrate causes the film to be subjected to compressive stress from the substrate. The in-plane cells are compressed, and correspondingly, the out-of-plane cells are elongated, increasing the out-of-plane interplanar spacing and causing the diffraction peaks to shift to lower angles. The other four diffraction peaks originate from the (l00) (l = 2, 4, 6, 8) crystal plane of the MgAl2O4 substrate, indicating that the prepared LiGa5O8 film... 0.9 (Ga 1-x Si x The 5O8 thin film is a highly preferentially oriented film, grown along the

[100] direction. Compared to the film prepared in Example 2 (x=0%), with the incorporation of Si, the diffraction peak corresponding to the (400) crystal plane shifts to a higher angle, and the higher the Si doping content, the greater the angle of rightward shift. This is due to the Ga on the tetrahedral coordination... 3+(0.47 Å) by Si with a smaller ionic radius 4+ The substitution of (0.26 Å) leads to cell shrinkage, a decrease in lattice constant, and a reduction in the interplanar spacing d of the (400) plane, causing the diffraction peaks to shift to higher angles. With increasing Si doping concentration, the diffraction peak intensity gradually weakens, and a new diffraction peak appears to the right of the (400) main peak. This is due to the reaction between Ga³⁺ and Si. 4 There is a significant difference in ionic radii between ⁺ and ⁺. Excessive Si doping induces lattice distortion, leading to a reduction in the stress on the film. In some regions, the stress is completely released, and the crystal structure reverts to a cubic phase, resulting in new diffraction peaks. Furthermore, the rocking curve of the (400) diffraction peak of the film shows that its full width at half maximum (FWHM) is between 0.032° and 0.549°, with a minimum value of 0.032°, indicating that all samples possess high crystallinity.

[0078] Figure 3 The Li prepared in Example 1 is given. 0.9 (Ga 0.93 Si 0.07 The atomic force microscopy image of the 5O8 thin film shows that the sample surface has an atomically smooth morphology with a root mean square roughness of only 0.3 nm.

[0079] Figure 4 The Li prepared in Example 1 is given. 0.9 (Ga 0.93 Si 0.07 A cross-sectional scanning electron microscope image of the 5O8 thin film sample. The image clearly shows that Li... 0.9 (Ga 0.93 Si 0.07 The thickness of the 5O8 thin film layer and the MgAl2O4 substrate layer was determined by calibrating the film thickness using a scale, and the thickness of the film was found to be approximately 147.6 nm.

[0080] Figure 5 Li₂ with different Si doping concentrations prepared in Examples 1-5 are given. 0.9 (Ga 1-x Si x The UV-Vis transmission spectrum of the 5O8 thin film. As can be seen from the figure, all Li... 0.9 (Ga 1-x Si x The 5O8 thin film exhibits an average transmittance of over 95% in the UV-VIS (300-600 nm) region and possesses a sharp absorption edge near 260 nm. This indicates that Li... 0.9 (Ga 1- x Si xThe 5O8 thin film exhibits high ultraviolet transmittance and excellent wavelength selectivity in the deep ultraviolet band below 260 nm, meeting the stringent detection requirements of solar-blind ultraviolet signals in engineering and defense applications. (Illustration shows Li...) 0.9 (Ga 1-x Si x (αhν) of 5O8 thin film 2 The linear fit of -(hν) is obtained by extrapolating (αhν). 2 The linear portion of the -(hν) curve is used to obtain the optical band gap E of the thin film. g The results showed that as the Si doping concentration increased, Li 0.9 (Ga 1-x Si x Optical band gap E of 5O8 thin film g The band gap gradually increases from 5.379 eV to 5.458 eV. This is considering the theoretical band gap E of SiO2. g The voltage is approximately 8.9 eV, therefore, after Si doping, Li 0.9 (Ga 1-x Si x Optical band gap E of 5O8 thin film g Increasing the Si doping content is reasonable, and the higher the Si doping content, the closer the band gap value of the film is to the optical band gap value of SiO2.

[0081] Figure 6 Li₂ with different Si doping concentrations prepared in Examples 1-5 are given. 0.9 (Ga 1-x Si x The IV characteristics of the 5O8 thin-film solar-blind ultraviolet photodetector under dark conditions and 254 nm ultraviolet illumination are shown in the figure. It can be seen from the figure that, under the same applied bias voltage, the intrinsic Li... 0.9 The Ga5O8 thin-film photodetector has a dark current of approximately 4 pA and low background noise, but its photocurrent is only 12 nA, resulting in an on / off ratio of only 3 × 10⁻⁶. 3 The responsivity is 0.037 mA / W, and the detectivity is 6.4 × 10⁻⁶. 9 Jones. When speaking to Li 0.9 After Si is doped into the Ga5O8 thin film, the dark current of the device remains essentially unchanged (approximately 4 × 10⁻⁶) under a bias voltage of 10 V. -12 A), and the photocurrent was significantly increased to the μA level, about 7 orders of magnitude higher than that of x=0 devices prepared under the same growth conditions, and its on / off ratio was also significantly improved accordingly. The Li prepared in Example 1 0.9 (Ga 0.93 Si 0.07 The 5O8 thin-film photodetector exhibits excellent performance: dark current as low as 4 pA, photocurrent up to 14 μA, and on / off ratio exceeding 10.6 The switching ratio compared to undoped Si Li 0.9 Ga5O8 thin-film devices showed a 1177-fold improvement; responsivity and detectivity reached 42 mA / W and 7.4 × 10⁻⁶, respectively. 12 Jones showed improvements of 1130 times and 1153 times compared to undoped devices, respectively. These results demonstrate that Si doping can effectively improve Li... 0.9 Overall performance of Ga5O8 thin-film photodetectors.

[0082] Figure 7 The Li prepared in Example 1 is given. 0.9 (Ga 0.93 Si 0.07 )5O8 thin-film photodetector and Li prepared in Example 2 0.9 The current-time (IT) characteristic curves and their fitting curves of the Ga5O8 thin-film photodetector are shown in the figure. It can be seen from the figure that the fast response rise time of the device in Example 2 is 0.275 s, the slow response rise time is 1.113 s, and the decay time is 0.024 s. In contrast, the fast response rise time of the device in Example 1 is 0.072 s, the slow response rise time is 0.601 s, and the decay time is 0.028 s. The decay times of the two devices are basically the same, but the corresponding rise time of the device in Example 1 is much shorter than that of the device in Example 2. Furthermore, the device in Example 1 can stably output a photocurrent of 12 μA under continuous switching, while the device in Example 2 can only stably output a photocurrent of 8 nA. In summary, the device prepared in Example 1 has a faster response speed, a larger photocurrent output, and more stable operation.

[0083] Figure 8 The Li prepared in Example 1 is given. 0.9 (Ga 0.93 Si 0.07 The graph shows the variation of photocurrent I of a 5O8 thin-film photodetector with incident light power density P under a bias voltage of 10 V, and its fitted curve. As can be seen from the graph, the photocurrent increases linearly with increasing incident light power density, and the fitted relationship is... This indicates that its response is nearly perfectly linear, demonstrating excellent characteristics and application potential for optical power detection.

[0084] Figure 9 The Li prepared in Example 1 is given. 0.9 (Ga 0.93 Si 0.07 )5O8 thin-film photodetector and Li prepared in Example 2 0.9 The responsivity of a Ga5O8 thin-film photodetector as a function of incident light power density. For undoped Li... 0.9Ga5O8 and Li doped with 7 mol% Si 0.9 (Ga 0.93 Si 0.07 The responsivity of the 5O8 thin-film photodetector increases with increasing optical power density, but the increasing trend gradually slows down. When the incident light power density is 3 mW / cm²... 2 At that point, the responsivity had already reached 42 mA / W. As the optical power density continued to increase, the responsivity remained essentially unchanged. Furthermore, Li... 0.9 (Ga 0.93 Si 0.07 The responsivity of 5O8 thin-film photodetectors is generally much higher than that of undoped Li. 0.9 The Ga5O8 device exhibits a maximum ratio of 1153 times, indicating that Si doping can significantly improve the device's responsivity.

[0085] The above embodiments are only used to further illustrate a Si-doped lithium gallium oxide thin film solar-blind ultraviolet detector and its preparation method according to the present invention. However, the present invention is not limited to the embodiments. Any simple modifications, alterations, substitutions, combinations, or simplifications made to the above embodiments based on the technical essence of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector, characterized in that, It includes a substrate layer from bottom to top, Li y (Ga 1-x Si x )5O8 thin film layer and metal electrode layer, wherein 0.01≤x≤0.07, 0.9≤y≤1.

1.

2. The Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector according to claim 1, characterized in that, The values ​​of x and y are 0.07 and 0.9, respectively.

3. The Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector according to claim 1, characterized in that, The substrate is a MgAl2O4 substrate, and the metal electrode layer is a gold electrode.

4. The Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector according to claim 3, characterized in that, The MgAl2O4 substrate is a single crystal of MgAl2O4 polished on one or both sides, with a size of 5-10 mm × 5-10 mm and a thickness of 0.2-1 mm. The gold electrode is an interdigitated gold electrode, wherein the finger width in the interdigitated electrode pattern is 100-500 μm, the finger spacing is 100-500 μm, and the finger length is 1.5-3 mm.

5. A method for fabricating a Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector according to any one of claims 1 to 4, characterized in that... Includes the following steps: Step 1. Mix SiO2, Li2CO3 and Ga2O3 raw material powders, and calcine them at 1200-1350℃ for 6-8 hours using a solid-state reaction method to obtain Li. y (Ga 1-x Si x 5O8 polycrystalline sputtering target, where x ranges from 0.01 to 0.07 and y ranges from 0.9 to 1.1; Step 2. Using pulsed laser deposition in an oxygen atmosphere, Li y (Ga 1-x Si x )5O8 polycrystalline target material, Li is grown on the substrate y (Ga 1-x Si x )5O8 thin film, wherein 0.01≤x≤0.07, 0.9≤y≤1.1, the film growth temperature is 550-650℃, and the oxygen partial pressure is 2.5-10 Pa; Step 3. In the Li y (Ga 1-x Si x The photodetector constructed by depositing a metal electrode on a 5O8 thin film to form a metal-semiconductor-metal planar electrode structure is the Si-doped lithium gallate thin film solar-blind ultraviolet detector.

6. The preparation method according to claim 5, characterized in that, The specific steps of step 1 include: S1, based on the chemical formula Li y (Ga 1-x Si x The amounts of SiO2, Li2CO3 and Ga2O3 polycrystalline powders were determined by 5O8, with x being 0.01-0.07 and y being 0.9-1.

1. S2. Place the SiO2, Li2CO3 and Ga2O3 polycrystalline powders weighed in step S1 into a ball mill jar, add anhydrous ethanol, and mix by ball milling. S3. Dry the powder that was uniformly mixed by ball milling in step S2, and pre-calcine it at 900-1000℃ in air atmosphere. After pre-calcinement, cool it to room temperature with the furnace, then grind the powder and sieve it to obtain Li. y (Ga 1-x Si x )5O8 powder; S4. The Li obtained in step S3 y (Ga 1-x Si x The 5O8 powder sample was placed in a ball mill jar, anhydrous ethanol was added, and it was ball milled a second time. S5. Mix the powder sample obtained in step S4 with polyvinyl alcohol aqueous solution, grind thoroughly and sieve, pour the sieved powder into an isostatic pressing mold and press it into a target blank. S6. Place the pressed target blank into a muffle furnace, first heat to 600℃, and remove the organic binder at 600℃ for 2 hours. Then heat to 1200-1350℃ and sinter for 6-8 hours. After furnace cooling, the Li is obtained. y (Ga 1-x Si x 5O8 target material.

7. The preparation method according to claim 5, characterized in that, In step 2, the pulsed laser energy density of the pulsed laser deposition method is 0.9-1.5 J / cm². 2 The pulsed laser frequency is 5-10 Hz, the number of pulses is 900-9000, the substrate temperature is 550-650℃, and the oxygen partial pressure is 2.5-10 Pa.

8. The preparation method according to claim 5, characterized in that, The specific steps of step 2 include: (1) The substrate is fixed to the heating plate with silver paste, and the Li y (Ga 1-x Si x The 5O8 target material is attached to the stainless steel target holder. The heating holder and the target material are placed together in the vacuum cavity of the pulsed laser deposition system, and the distance between the substrate and the target material is set to 4-5 cm. (2) Use a dry pump to evacuate the gas pressure inside the cavity to below 10 Pa, and then use a molecular pump to evacuate the vacuum to 10 Pa. -4 Below Pa; (3) Turn on the laser heater to heat the substrate to 550-650℃ and maintain the temperature constant; (4) Close the slide valve, turn on the gas flow controller to introduce oxygen into the cavity, and use the side valve to fine adjust the gas pressure in the cavity to maintain the background oxygen partial pressure in the cavity at 2.5-10 Pa. (5) Use a baffle to block the heating support, and set the ceramic target to move along the x-axis and y-axis at a speed of 0.01-0.3 mm / s. Set the pulsed laser energy density to 0.9-1.5 J / cm². 2 The pulsed laser frequency is 5-10 Hz, the number of pulses is 900-9000, the laser is turned on, and the target material is pre-sputtered for 3-10 minutes; (6) After the pre-sputtering is completed, the heating holder is set to rotate at a speed of 3-10 rpm, and then the baffle is removed to start the epitaxial growth of the thin film on the substrate; (7) After deposition, maintain the background oxygen partial pressure at 2.5-10 Pa and cool down at a rate of 10-50 ℃ / min; (8) Lower the temperature inside the cavity to below 200°C, turn off the molecular pump and the dry pump, introduce nitrogen into the vacuum cavity to bring the pressure inside the cavity back to atmospheric pressure, remove the heating holder, and obtain the Li. y (Ga 1-x Si x )5O8 film.

9. The preparation method according to claim 5, characterized in that, In step 3, a small ion sputtering instrument and a custom-made mask are used on the Li y (Ga 1-x Si x Metal electrodes were deposited on 5O8 thin films. When using a small ion sputtering instrument, the cavity pressure was set to 6-12 Pa, the current to 6-12 mA, and the time to 120-240 s.

10. The application of the Si-doped lithium gallium oxide thin-film solar-blind ultraviolet detector according to any one of claims 1 to 4 in the field of solar-blind ultraviolet signal detection.

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