Mg-doped gallium oxide film, preparation method and application thereof, and solar blind ultraviolet photodetector

Abstract

The application provides a Mg-doped gallium oxide film and a preparation method and application thereof, and a solar blind ultraviolet photodetector. The application uses a low-cost CVD technology to prepare the Mg-doped gallium oxide film, and compared with pure gallium oxide, the Mg doping effectively reduces Vo oxygen defects, increases a forbidden band width, and further reduces the capture of carriers by deep energy level defects, so that the photoelectric detection performance is greatly improved. Compared with pure gallium oxide, the light / dark current ratio is significantly improved to 10 6 , and the detection rate reaches 1.576*10 14 Jones. The response time is improved from the original rise of 318.1 ms and the fall of 187.5 ms to the rise of 14.7 ms and the fall of 7 ms. The obvious decrease of the dark current and the response time greatly reduces the power consumption in the non-working condition and improves the sensitivity to ultraviolet light stimulation. In addition, the prepared film is subjected to dot ultraviolet imaging research, and it is found that the film can present a relatively clear letter image.

Description

Technical Field

[0001] This invention relates to the field of photodetector technology, and in particular to a Mg-doped gallium oxide thin film, its preparation method and application, and a solar-blind ultraviolet photodetector. Background Technology

[0002] The strong absorption of solar radiation with wavelengths below 280 nm by the atmospheric ozone layer endows solar-blind ultraviolet photodetectors (SBPDs) with extremely low background noise and high reliability. SBPDs have been applied in various fields, including ultraviolet detection, flame detection, missile guidance systems, and underwater communications. With the rapid development of third-generation semiconductor technology, wide-bandgap semiconductor materials have become the research focus of next-generation optoelectronic devices due to their excellent photoelectric conversion performance and adaptability to extreme environments. Among them, gallium oxide (Ga2O3) is considered the most promising candidate material for SBPDs due to its spectral response range that is highly matched with the solar-blind ultraviolet band, its theoretical breakdown electric field strength of 8 MV / cm, and its good thermal stability. However, gallium oxide materials inevitably contain oxygen defects and interstitial gallium defects, leading to problems such as increased dark current, reduced response speed, and decreased uniformity and reliability of SBPD devices.

[0003] Recently, solar-blind photodetectors (SBPDs) based on Ga2O3 have been extensively studied and reported. For example, existing technologies disclose the preparation of a series of different Mg2O3-based SBPDs using the sol-gel method. 2+ The doping concentration of Ga2O3 thin films effectively modulates the bandgap and photoelectric properties, with the device exhibiting an optimal doping concentration of 4.2% and a bandgap of 2.6 × 10⁻⁶. 3 The photocurrent-to-dark-current ratio is 4.57 × 10⁻⁶. 12 The specific detectivity is high. However, its response time is as high as 0.91s (rise) / 1.2s (fall). Although the above methods have modified the gallium oxide thin film and achieved relatively superior photoelectric detection performance, they cannot simultaneously achieve key parameters such as detectivity and response speed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a Mg-doped gallium oxide thin film, its preparation method, and its application in a solar-blind ultraviolet photodetector. This invention utilizes a low-cost CVD technique to prepare the Mg-doped gallium oxide thin film. Compared to pure gallium oxide, Mg doping effectively reduces Vo-oxygen defects, increases the bandgap, and consequently reduces carrier trapping by deep-level defects, significantly improving photodetector performance. Compared to pure gallium oxide, the photocurrent-to-dark-current ratio is improved from 10... 4 Increase to 10 6 The dark current was significantly reduced by about three orders of magnitude, and the detectivity increased to 1.576 × 10⁻⁶. 14Jones improved the response time from 318.1 ms up and 187.5 ms down to 14.7 ms up and 7 ms down. This significant reduction in dark current and response time greatly lowers power consumption in non-operating conditions and improves sensitivity to UV light stimulation.

[0005] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a Mg-doped gallium oxide thin film, comprising the following steps:

[0007] Gallium oxide, magnesium oxide, and carbon powder are mixed to obtain a mixed powder;

[0008] The mixed powder is placed inside a quartz boat, and a substrate is placed inside the quartz boat above the mixed powder;

[0009] The quartz boat is transferred to a chemical vapor deposition tube furnace, the air inside the tube furnace is vented, and then an argon-oxygen mixture is introduced to heat the tube furnace to 850–950°C and hold it at that temperature to deposit a Mg-doped gallium oxide thin film on the substrate.

[0010] Preferably, the molar ratio of gallium oxide, magnesium oxide and carbon powder is (30-40):(1-1.5):(80-100).

[0011] Preferably, the tubular furnace is heated to 850-950°C at a rate of 10-15°C / min and held at that temperature for 90-150 min.

[0012] Preferably, in the step of introducing the argon-oxygen mixture, the argon flow rate is 150-160 sccm and the oxygen flow rate is 1-2 sccm.

[0013] Preferably, the quartz boat is transferred to a chemical vapor deposition tube furnace, and a protective gas is introduced into the tube furnace to purge the air inside the furnace.

[0014] The protective gas is argon, and the flow rate of the protective gas is 400-450 sccm.

[0015] Preferably, before placing the substrate in the quartz boat, the substrate is further cleaned, specifically by placing the substrate in water, acetone, and ethanol in sequence for ultrasonic treatment.

[0016] Preferably, the substrate includes any one of a sapphire substrate, a gallium nitride substrate, and a gallium oxide substrate.

[0017] Secondly, the present invention also provides a Mg-doped gallium oxide thin film, which is prepared by the aforementioned preparation method.

[0018] Thirdly, the present invention also provides a method for preparing a Mg-doped gallium oxide thin film or the application of the Mg-doped gallium oxide thin film in the preparation of a solar-blind ultraviolet photodetector.

[0019] Fourthly, the present invention also provides a solar-blind ultraviolet photodetector, the preparation method of which includes the following steps:

[0020] Mg-doped gallium oxide thin films were prepared according to the preparation method described above.

[0021] Interdigitated electrodes are fabricated on the surface of a Mg-doped gallium oxide thin film using an interdigitated electrode mask, thus obtaining a solar-blind ultraviolet photodetector.

[0022] Preferably, the material of the interdigitated electrode is Au;

[0023] The interdigitated electrode has 4 to 8 pairs of interdigitated fingers, an interdigitated finger width of 0.8 to 1.2 mm, an interdigitated finger spacing of 30 to 60 μm, and an interdigitated finger length of 0.4 to 0.8 cm.

[0024] The thickness of the interdigitated electrodes is 60–120 nm.

[0025] The Mg-doped gallium oxide thin film, its preparation method, and its application, as well as the solar-blind ultraviolet photodetector of the present invention, have the following advantages compared with the prior art:

[0026] The present invention discloses a method for preparing Mg-doped gallium oxide thin films using low-cost CVD technology. Compared to pure gallium oxide, the photocurrent-to-dark-current ratio is significantly improved to 10. 6 The detection rate reached 1.576×10 14 Jones. The response time was improved from 318.1 ms rise and 187.5 ms fall to 14.7 ms rise and 7 ms fall. The significant reduction in dark current and response time greatly reduced power consumption in non-operating conditions and improved sensitivity to ultraviolet light stimulation. In addition, the prepared thin film was studied by dotted ultraviolet imaging and it was found that it can present relatively clear letter images. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of the interdigitated electrode of the present invention;

[0029] Figure 2 This is a cross-sectional EDS image of the Mg-doped gallium oxide thin film prepared in Example 1;

[0030] Figure 3 The XRD patterns are those of the Mg-doped gallium oxide thin film prepared in Example 1 and the gallium oxide thin film prepared in Comparative Example 1.

[0031] Figure 4 X-ray photoelectron spectroscopy (XPS) spectra of undoped and Mg-doped gallium oxide thin films prepared in Example 1;

[0032] Figure 5 The semi-log current-voltage (IV) characteristic curves of a solar-blind ultraviolet photodetector prepared using pure gallium oxide thin film in Comparative Example 1 under different light intensities of ultraviolet light in darkness and under 254 nm illumination.

[0033] Figure 6 The semi-log current-voltage (IV) characteristic curves of the solar-blind ultraviolet photodetector prepared using Mg-doped gallium oxide thin film in Example 1 under different light intensities of ultraviolet light in darkness and under 254nm illumination.

[0034] Figure 7 The normalized time response characteristic curves of the solar-blind ultraviolet photodetectors in Example 1 and Comparative Example 1 are shown.

[0035] Figure 8 This is the long-term light response curve of the solar-blind ultraviolet photodetector in Example 1;

[0036] Figure 9 The middle section shows a performance comparison of the solar-blind ultraviolet photodetectors in Example 1 and Comparative Example 1;

[0037] Figure 10 This is a structural test diagram of the single-point imaging capability of the photodetector prepared in Embodiment 1 of the present invention. Detailed Implementation

[0038] To facilitate understanding of the present invention, a more comprehensive description of the invention will be provided below in conjunction with specific embodiments. Preferred embodiments of the invention are given in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0039] The order in which the embodiments are described below is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0040] This invention provides a method for preparing Mg-doped gallium oxide thin films, comprising the following steps:

[0041] S1. Mix gallium oxide, magnesium oxide, and carbon powder to obtain a mixed powder;

[0042] S2. Place the mixed powder in a quartz boat and place a substrate in the quartz boat above the mixed powder;

[0043] S3. Transfer the quartz boat to a chemical vapor deposition tube furnace, purge the air from the tube furnace, then introduce an argon-oxygen mixture to heat the tube furnace to 850-950°C and hold it at that temperature to deposit a Mg-doped gallium oxide thin film on the substrate.

[0044] The method for preparing Mg-doped gallium oxide thin films of the present invention utilizes low-cost CVD technology to achieve the preparation of Mg-doped gallium oxide thin films. Compared with pure gallium oxide, Mg doping effectively reduces Vo oxygen defects (defects formed by the absence of oxygen atoms in the oxide crystal structure, where Vo is an abbreviation for Vacancy of oxygen), increases the band gap, and thus reduces the trapping of charge carriers by deep-level defects, resulting in a significant improvement in photoelectric detection performance. Compared with pure gallium oxide, the photocurrent-to-dark-current ratio is significantly improved to 10. 6 The detection rate reached 1.576×10 14 Jones. The response time was improved from 318.1 ms rise and 187.5 ms fall to 14.7 ms rise and 7 ms fall. The significant reduction in dark current and response time greatly reduced power consumption in non-operating conditions and improved sensitivity to ultraviolet light stimulation. In addition, the prepared thin film was studied by dotted ultraviolet imaging and it was found that it can present relatively clear letter images.

[0045] Specifically, the principle of this invention is as follows:

[0046] Ga2O3(s)+2C(s)→Ga2O(v)+2CO(g)

[0047] Ga2O3(s)+3C(s)→2Ga(v)+3CO(g)

[0048] MgO(s) + C(s) → Mg(v) + CO(g)

[0049] Carbon powder reduces gallium oxide and magnesium oxide respectively to obtain gaseous forms of Ga2O, Ga, and Mg. The three vapors are deposited on the substrate. Oxygen is introduced into the reaction gas. The oxygen can react with the three vapors at high temperature to form a gallium oxide film. Because the content of Mg is very small, no MgO impurities are generated. Instead, Mg is doped into gallium oxide to fill the inherent defects in the gallium oxide film.

[0050] In some embodiments, the molar ratio of gallium oxide, magnesium oxide, and carbon powder is (30-40):(1-1.5):(80-100).

[0051] In some embodiments, the tubular furnace is heated to 850–950°C at a rate of 10–15°C / min and held at that temperature for 90–150 min.

[0052] In some embodiments, during the step of introducing the argon-oxygen mixture, the argon flow rate is 150–160 sccm and the oxygen flow rate is 1–2 sccm.

[0053] In some embodiments, the quartz boat is transferred to a chemical vapor deposition tube furnace, and a protective gas is introduced into the tube furnace to purge the air inside the tube furnace;

[0054] The protective gas is argon, and the flow rate of the protective gas is 400-450 sccm.

[0055] In some embodiments, before placing the substrate in the quartz boat, the substrate is further cleaned, specifically by placing the substrate in water, acetone and ethanol in sequence for ultrasonic treatment, with each ultrasonic treatment lasting 20 to 30 minutes.

[0056] In some embodiments, the substrate includes any one of a sapphire substrate, a gallium nitride substrate, and a gallium oxide substrate. Specifically, the sapphire substrate is a c-plane sapphire substrate.

[0057] Based on the same inventive concept, the present invention also provides a Mg-doped gallium oxide thin film, which is prepared by the aforementioned preparation method.

[0058] Based on the same inventive concept, the present invention also provides an application of the above-mentioned preparation method to prepare Mg-doped gallium oxide thin films or the above-mentioned Mg-doped gallium oxide thin films in the preparation of solar-blind ultraviolet photodetectors.

[0059] Based on the same inventive concept, the present invention also provides a solar-blind ultraviolet photodetector, the preparation method of which includes the following steps:

[0060] Mg-doped gallium oxide thin films were prepared according to the above preparation method;

[0061] Interdigitated electrodes are fabricated on the surface of a Mg-doped gallium oxide thin film using an interdigitated electrode mask, thus obtaining a solar-blind ultraviolet photodetector.

[0062] In some embodiments, the material of the interdigital electrode is Au, that is, the interdigital electrode is an Au interdigital electrode, the number of interdigital pairs of the interdigital electrode is 4 to 8, the interdigital width is 0.8 to 1.2 mm, the interdigital spacing is 30 to 60 μm, and the interdigital length is 0.4 to 0.8 cm;

[0063] The thickness of the interdigitated electrodes is 60–120 nm.

[0064] For details, please refer to Figure 1 As shown, the interdigitated electrode includes a first interdigitated metal Au electrode 5 and a second interdigitated metal Au electrode 6. The first interdigitated metal Au electrode 5 includes a first electrode 2 and a first interdigitated finger 1, with one end of the first interdigitated finger 1 perpendicularly connected to the first electrode 2. The second interdigitated metal Au electrode 6 includes a second electrode 3 and a second interdigitated finger 4, with one end of the second interdigitated finger 4 perpendicularly connected to the second electrode 3. The first interdigitated finger 1 is located between two adjacent second interdigitated fingers 4, and the second interdigitated finger 4 is located between two adjacent first interdigitated fingers 1, i.e., the first interdigitated fingers 1 and the second interdigitated fingers 4 are staggered. The number of interdigitated finger pairs is 4 to 8, i.e., the number of first interdigitated fingers 1 is 4 to 8, and the number of second interdigitated fingers 4 is 4 to 8. The width of the interdigitated fingers is 0.8–1.2 mm, that is, the width of the first interdigitated finger 1 is 0.8–1.2 mm, and the width of the second interdigitated finger 4 is 0.8–1.2 mm; the interdigitated finger spacing is 30–60 μm, that is, the spacing between two adjacent first interdigitated fingers 1 is 30–60 μm, and the spacing between two adjacent second interdigitated fingers 4 is 30–60 μm; the interdigitated finger length is 0.4–0.8 cm, that is, the length of the first interdigitated finger 1 is 0.4–0.8 cm, and the length of the second interdigitated finger 4 is 0.4–0.8 μm; the thickness of the interdigitated finger electrodes is 60–120 nm, that is, the thickness of the first electrode 2, the first interdigitated finger 1, the second electrode 3, and the second interdigitated finger 4 is all 60–120 nm.

[0065] Metal-semiconductor (MSM) devices are fabricated by growing Au interdigitated electrodes using a thermal evaporation apparatus; these devices are solar-blind ultraviolet photodetectors.

[0066] The following further illustrates the Mg-doped gallium oxide thin film, its preparation method, and applications, as well as solar-blind ultraviolet photodetectors, of the present invention with specific embodiments. This section further describes the content of the present invention in conjunction with specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0067] Example 1

[0068] This embodiment provides a method for preparing Mg-doped gallium oxide thin films, including the following steps:

[0069] This invention provides a method for preparing Mg-doped gallium oxide thin films, comprising the following steps:

[0070] S1. Mix gallium oxide, magnesium oxide and carbon powder in a molar ratio of 35:1:90 to obtain a mixed powder;

[0071] S2. The c-plane sapphire substrate is placed in water, acetone and ethanol in sequence for ultrasonic treatment, and then dried with nitrogen for later use. The ultrasonic treatment time for each stage is 30 minutes.

[0072] The mixed powder is placed inside a quartz boat, and a substrate is placed inside the quartz boat above the mixed powder;

[0073] S3. Transfer the quartz boat to a chemical vapor deposition tube furnace. Introduce a protective gas into the tube furnace to purge the air inside. The protective gas is argon, the flow rate is 400 sccm, and the introduce time is 25 min.

[0074] Then, an argon-oxygen mixture is introduced into the tube furnace, and the furnace is heated to 950°C at a rate of 10°C / min and held for 90 min to deposit a Mg-doped gallium oxide film on the substrate. In the step of introducing the argon-oxygen mixture, the argon flow rate is 150 sccm and the oxygen flow rate is 1 sccm.

[0075] This embodiment also provides a solar-blind ultraviolet photodetector, the preparation method of which includes the following steps:

[0076] A Mg-doped gallium oxide thin film was prepared according to the preparation method in Example 1 above;

[0077] Using an interdigitated electrode mask, an 80 nm thick Au interdigitated electrode is grown on the surface of a Mg-doped gallium oxide thin film using a thermal evaporation apparatus to fabricate a metal-semiconductor-metal (MSM) device, namely a solar-blind ultraviolet photodetector. The interdigitated electrode has 6 pairs of interdigitates, an interdigitate width of 1 mm, an interdigitate spacing of 49 μm, and an interdigitate length of 0.5 cm. The thickness of the interdigitated electrode is 80 nm.

[0078] Comparative Example 1

[0079] This comparative example provides a method for preparing gallium oxide thin films, similar to Example 1, except that magnesium oxide is not added during the preparation process; specifically, it includes the following steps:

[0080] S1. Mix gallium oxide and carbon powder in a molar ratio of 1:2.5 to obtain a mixed powder;

[0081] S2. The c-plane sapphire substrate is placed in water, acetone and ethanol in sequence for ultrasonic treatment, and then dried with nitrogen for later use. The ultrasonic treatment time for each stage is 30 minutes.

[0082] The mixed powder is placed inside a quartz boat, and a substrate is placed inside the quartz boat above the mixed powder;

[0083] S3. Transfer the quartz boat to a chemical vapor deposition tube furnace. Introduce a protective gas into the tube furnace to purge the air inside. The protective gas is argon, the flow rate is 400 sccm, and the introduce time is 25 min.

[0084] Then, an argon-oxygen mixture is introduced into the tube furnace, and the furnace is heated to 950°C at a rate of 10°C / min and held for 90 min to deposit a gallium oxide film on the substrate. In the step of introducing the argon-oxygen mixture, the argon flow rate is 150 sccm and the oxygen flow rate is 1 sccm.

[0085] This embodiment also provides a solar-blind ultraviolet photodetector, the preparation method of which includes the following steps:

[0086] Gallium oxide thin films were prepared according to the preparation method in Comparative Example 1 above;

[0087] Using an interdigitated electrode mask, an 80 nm thick Au interdigitated electrode is grown on the surface of a gallium oxide thin film using a thermal evaporation apparatus to fabricate a metal-semiconductor-metal (MSM) device, namely a solar-blind ultraviolet photodetector. The interdigitated electrode has 6 pairs of interdigitates, an interdigitate width of 1 mm, an interdigitate spacing of 49 μm, and an interdigitate length of 0.5 cm. The thickness of the interdigitated electrode is 80 nm.

[0088] Performance Characterization

[0089] Figure 2 The images show cross-sectional EDS images of the Mg-doped gallium oxide thin film prepared in Example 1, characterizing the content and distribution of various elements. Brownish-yellow and red represent the distribution of Ga and O in the shown film cross-sections. These images demonstrate a sufficient and uniform distribution of Ga and O. Because a C-plane sapphire substrate was used, the oxygen content of the substrate is more pronounced in the images shown. Purple represents the distribution of Mg, indicating that Mg is effectively doped into the gallium oxide thin film.

[0090] Figure 3 The images show the XRD patterns of the Mg-doped gallium oxide thin film prepared in Example 1 and the gallium oxide thin film prepared in Comparative Example 1. Figure 3 In this context, Pure represents the gallium oxide thin film prepared in Comparative Example 1, and Mg doped Ga2O3 represents the Mg-doped gallium oxide thin film prepared in Example 1.

[0091] from Figure 3 As can be seen, the sharp XRD diffraction peaks at 19.0°, 38.4°, and 59.2° correspond to interplanar spacings of (-201), (-402), and (-603), respectively, indicating that the film is β-phase gallium oxide. The peak of β-Ga₂O₃:Mg matches that of the undoped gallium oxide film, and there are no additional peaks corresponding to impurities such as MgO or MgGaO, proving that this preparation method produces a Mg-doped gallium oxide film.

[0092] Figure 4 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the Mg-doped gallium oxide thin film prepared in Example 1. The detected Mg 1s core level provides further evidence for the successful doping of Mg into the Ga2O3 thin film. All the above characterizations further demonstrate that the thin film prepared by the above method is Mg-doped β-Ga2O3, and there are no other impurity phases or alloys present.

[0093] To investigate the effect of Mg doping on photodetector performance, the semi-logarithmic current-voltage (IV) characteristics of the solar-blind ultraviolet photodetectors prepared in Example 1 and Comparative Example 1 were tested under darkness and 254 nm light intensity excitation. Figures 5-6 As shown.

[0094] Figure 5 A solar-blind ultraviolet photodetector prepared using a pure gallium oxide thin film as a comparative example 1 was tested under different light intensities (1000 μW / cm²) in darkness and under 254 nm illumination. 2 500μW / cm 2 250μW / cm 2 150μW / cm 2 50μW / cm 2 20μW / cm 2 10μW / cm 2 A comparison of the semi-logarithmic current-voltage (IV) characteristic curves under ultraviolet light.

[0095] Figure 6 The solar-blind ultraviolet photodetector prepared using a Mg-doped gallium oxide thin film in Example 1 was tested under different light intensities (1000 μW / cm²) in darkness and under 254 nm illumination. 2500μW / cm 2 250μW / cm 2 150μW / cm 2 50μW / cm 2 20μW / cm 2 10μW / cm 2 A comparison of the semi-logarithmic current-voltage (IV) characteristic curves under ultraviolet light.

[0096] from Figures 5-6 As can be seen, the dark current of the solar-blind ultraviolet photodetector exhibits significant changes under dark conditions, while at 10 μW / cm 2 Under solar-blind ultraviolet light irradiation, the solar-blind ultraviolet photodetector prepared by Mg-doped gallium oxide film in Example 1 showed a slightly lower photocurrent compared to the solar-blind ultraviolet photodetector prepared by pure gallium oxide film in Comparative Example 1. The solar-blind ultraviolet photodetector prepared by pure gallium oxide film in Comparative Example 1 exhibited high leakage current, which is related to the concentration of Vo in the film. When Mg is doped, the concentration of Vo decreases, and the dark current (Idark) decreases. The Idark of the solar-blind ultraviolet photodetector prepared by Mg-doped gallium oxide film in Example 1 is 2.67 × 10⁻⁶ at 20 V. -12 A) The Idark level is approximately three orders of magnitude lower than that of the solar-blind ultraviolet photodetector fabricated using pure gallium oxide thin films in Comparative Example 1. This lower Idark level can be attributed to the reduction in defect concentration.

[0097] from Figures 5-6 As can be seen, both the solar-blind ultraviolet photodetectors in Example 1 and Comparative Example 1 exhibit good photodetector performance, showing a relatively obvious gradient change. The photocurrent of both increases continuously with increasing light intensity and voltage. The reason for the voltage-dependent change is that a higher voltage results in a higher electric field, allowing for the collection of more charge carriers. It can be seen that the dark current of the solar-blind ultraviolet photodetector after Mg doping is significantly reduced by approximately three orders of magnitude; the dark current of the doped device at 20V is 2.67 × 10⁻⁶. -12 A.

[0098] Figure 7 The time response characteristics of the solar-blind ultraviolet photodetectors in Example 1 and Comparative Example 1 are shown. Rise time is defined as the time required for the photocurrent to increase from 10% to 90% of its maximum value. Correspondingly, decay time is defined as the time taken for the photocurrent to decrease from 90% to 10% of its maximum value. For comparison, the normalized time response characteristics of these devices are shown as follows: Figure 7As shown in the figure, the results indicate that the solar-blind ultraviolet photodetector prepared with pure gallium oxide thin film in Comparative Example 1 has longer rise and fall times, tr: 318.1 ms and td: 187.5 ms, respectively. In contrast, the solar-blind ultraviolet photodetector prepared with Mg-doped gallium oxide thin film in Example 1 has rise and fall times of tr: 14.7 ms and td: 7 ms, respectively, which are significantly better than the undoped device.

[0099] To evaluate the repeatability of the solar-blind ultraviolet photodetector after Mg doping in Example 1, its photoresponse was characterized over a longer period of time, such as... Figure 8 As shown. Figure 8 As shown in V ds =1.5V (i.e., an external bias voltage of 1.5V is applied to the first interdigitated metal Au electrode 5 (as the source) and the second interdigitated metal Au electrode 6 (as the drain)), with a light intensity of 1000μW / cm. 2 Under these conditions, the solar-blind ultraviolet photodetector fabricated from the Mg-doped gallium oxide thin film in Example 1 was subjected to periodic on / off switching. It was found that the device current did not exhibit any significant degradation within the studied period. This observation highlights the stable and reliable performance of the device under such repeated photoactivation, making it highly promising for practical applications.

[0100] Figure 9 In Figure (a), the responsivity (A / W), detectivity, and light intensity (20V bias) of the solar-blind ultraviolet photodetector prepared using a Mg-doped gallium oxide thin film in Example 1 are shown. Figure 9 As shown in (a), both responsivity and detectivity increase with decreasing optical power, indicating that the solar-blind ultraviolet photodetector has good performance under weak light intensity (10 μW / cm). 2 The detector's detectivity reaches 1.576 × 10⁻⁶ under illumination. 14 Jones.

[0101] To evaluate the effect of applied bias voltage on the performance of the solar-blind ultraviolet photodetector prepared using a Mg-doped gallium oxide thin film in Example 1, a 254 nm, 10 μW / cm² photodetector was tested under different applied bias voltages. 2 When light shines onto the photodetector, such as... Figure 9 As shown in (b), the detectivity increases from 2.91 × 10⁻⁶ as the bias voltage increases (from 4V to 20V). 13 Jones increased linearly to 1.576 × 10 14 Jones. Higher bias accelerates the extraction of more photogenerated carriers, resulting in a higher detectivity.

[0102] Furthermore, the external quantum efficiency (EQE) of the solar-blind ultraviolet photodetector in Example 1 was calculated using the formula EQE = hcRl / ql, where h is Planck's constant, c is the speed of light, l is the illumination wavelength, R is the responsivity, and q represents the electron charge. Figure 9 As shown in (b), with the increase of the applied bias voltage (from 4V to 20V), the EQE increases linearly from 55.4% to 433.3% (at a light intensity of 10μW / cm²). 2 At a bias voltage of 20V, the EQE result is significantly higher than 100%, indicating that the solar-blind ultraviolet photodetector of this invention has a large internal gain.

[0103] Figure 9 Images (c) and (d) show a comparison of the PDCR (on / off ratio, calculated from (photocurrent - dark current) / divity) of the solar-blind ultraviolet photodetector (Mg-doped) prepared using a Mg-doped gallium oxide thin film in Example 1 and the solar-blind ultraviolet photodetector (pure) prepared using a pure gallium oxide thin film in Comparative Example 1, under different light intensities at 20V. Figure 9 As can be seen from (c) and (d), under the same conditions, the photoelectric detection performance of the Mg-doped detector is much better than that of the undoped detector. This indicates that Mg doping can improve the photoelectric detection performance of the device.

[0104] Table 1 below shows the performance of the solar-blind ultraviolet photodetector prepared by Mg-doped gallium oxide thin film in Example 1.

[0105] Table 1 - Performance of the solar-blind ultraviolet photodetector prepared from Mg-doped gallium oxide thin films in Example 1

[0106]

[0107] The photocurrent in Table 1 is calculated at a bias voltage of 20V and a value of 1000μW / cm. 2 The photocurrent obtained under the light intensity was 1.01 × 10⁻⁶. -5 A; When biased at 20V, 1000μW / cm 2 The on / off ratio calculated under the given light intensity is 3.78 × 10⁻⁶. 6 Both responsivity and detectivity are achieved at a bias voltage of 20V and a voltage of 1000μW / cm. 2 The results were calculated based on the light intensity.

[0108] This invention also constructs an imaging system to test the single-point imaging capability of the solar-blind ultraviolet photodetector prepared from the Mg-doped gallium oxide thin film in Example 1. The ultraviolet photodetector imaging system mainly consists of an ultraviolet lamp, a cutout pattern, an ultraviolet photodetector, a data acquisition system, a cross-shaped sliding stage, and a host computer, etc. (e.g., ...) Figure 10 (As shown in (a)). The hollowed-out pattern uses the letters H, U, and I to represent the differentiated perception and analysis of the target information. The scanning area consists of 1600 points in a 40×40 area. Figure 10 In the middle (b), the scanned image is displayed with different current brightness levels, and it can be clearly seen that all the letters can be clearly identified. Figure 10 In diagram (c), the minimum photocurrent is set as the switching value to clearly display all identifiable points. It can be seen that the three letters H, U, and I are clearly displayed, but noise points are still identified in the area surrounding the letters. Based on the above exploration of single-point imaging capabilities, the potential of the solar-blind ultraviolet photodetector prepared from the Mg-doped gallium oxide thin film of this invention in ultraviolet single-point imaging applications is evident.

[0109] It is understood that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0110] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.

Claims

1. A solar-blind ultraviolet photodetector, characterized in that, The method for preparing the solar-blind ultraviolet photodetector includes the following steps: Mg-doped gallium oxide thin films were prepared. Using an interdigitated electrode mask, interdigitated electrodes are fabricated on the surface of a Mg-doped gallium oxide thin film, thus obtaining a solar-blind ultraviolet photodetector. The material of the interdigitated electrodes is Au; The interdigitated electrode has 6 pairs of interdigitated fingers, an interdigitated finger width of 1 mm, an interdigitated finger spacing of 49 μm, and an interdigitated finger length of 0.5 cm. The thickness of the interdigitated electrodes is 80 nm; The method for preparing the Mg-doped gallium oxide thin film includes the following steps: Gallium oxide, magnesium oxide, and carbon powder are mixed to obtain a mixed powder; The mixed powder is placed inside a quartz boat, and a substrate is placed inside the quartz boat above the mixed powder; The quartz boat was transferred to a chemical vapor deposition tube furnace, the air inside the tube furnace was vented, and then an argon-oxygen mixture was introduced. The tube furnace was heated to 950°C at 10°C / min and held for 90 min to deposit a Mg-doped gallium oxide thin film on the substrate. The molar ratio of gallium oxide, magnesium oxide, and carbon powder is 35:1:90; In the step of introducing the argon-oxygen mixture, the argon flow rate is 150~160 sccm and the oxygen flow rate is 1~2 sccm.

2. The solar-blind ultraviolet photodetector as described in claim 1, characterized in that, The quartz boat is transferred to a chemical vapor deposition tube furnace, and a protective gas is introduced into the tube furnace to purge the air inside. The protective gas is argon, and the flow rate of the protective gas is 400~450 sccm.

3. The solar-blind ultraviolet photodetector as described in claim 1, characterized in that, Before placing the substrate in the quartz boat, the substrate is also cleaned, specifically by sequentially placing the substrate in water, acetone and ethanol for ultrasonic treatment. The substrate includes any one of sapphire substrate, gallium nitride substrate, and gallium oxide substrate.

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