A self-powered solar-blind ultraviolet detector and its preparation method

Abstract

A self-powered day-blind ultraviolet detector and a preparation method thereof, belonging to the field of photoelectric detector preparation, the specific scheme is as follows: a self-powered day-blind ultraviolet detector, comprising a substrate, a film a and a film b, wherein the film a is grown on the substrate, the film b is grown on the film a, electrodes are arranged on the film a and the film b are both (In x Ga 1‑x ) 2 O 3 The material has different contents of In components in the film a and the film b. In the detector, due to different growth temperatures of magnetron sputtering, the film a2 and the film b3 have different contents of In components, thus having different bandgap widths, generating a built-in electric field to obtain a self-powered detector, and the preparation method is simple and easy to operate, low in cost, easy to implement, and easy to promote.

Description

Technical Field

[0001] The invention belongs to the field of photoelectric detector preparation, and in particular relates to a self-powered solar-blind ultraviolet detector and a preparation method thereof. Background Art

[0002] The detection band of solar-blind UV detectors is 200nm-280nm. Solar radiation in this band will be strongly absorbed by the ozone layer, and the intensity on the earth's surface is almost zero, resulting in extremely low background noise for solar-blind UV detectors, whether during the day or at night, outdoors or indoors, and almost unaffected by sunlight. Therefore, solar-blind UV detectors have extremely high sensitivity and all-weather detection capabilities that visible-blind UV detectors and infrared detectors do not have. In addition, almost all objects have infrared radiation characteristics, while solar-blind UV radiation is not an inherent characteristic of all objects, which results in solar-blind UV detectors having extremely low false alarm rates compared to infrared detectors.

[0003] At present, commercial solar-blind UV detectors are mainly silicon-based charge-coupled devices (CCDs) and photomultiplier tubes. They have low dark current and fast response capabilities in the ultraviolet band, but they also have many disadvantages: Since the detection band of CCD is wide, covering the ultraviolet, visible and infrared bands, in order to increase the ultraviolet-visible spectral selectivity of the detector, expensive high-transmittance filters are needed to filter the visible and infrared bands, which increases the cost and size of the detector; in addition, under high temperature conditions, the detection performance of CCD is significantly reduced, mainly reflected in the decrease in efficiency and the increase in dark current. Photomultiplier tubes need to maintain vacuum and apply a large bias voltage, which places stringent requirements on the packaging of the device and consumes a lot of energy; and photomultiplier tubes also have the disadvantages of large size and fragility. The above disadvantages of CCD and photomultiplier tubes limit their development.

[0004] Wide-bandgap semiconductor UV detectors have inherent UV characteristics and do not require filters during detection. Among them, wide-bandgap semiconductor materials used for solar-blind UV band detection mainly include AlGaN, diamond, MgZnO and Ga2O3. Due to the serious self-compensation effect, these semiconductor materials have the problem of difficulty in preparing p-type materials. Therefore, ohmic contacts or Schottky contacts formed by metal / semiconductors are mostly used to realize photoconductive or photovoltaic detectors, and these detectors require external voltage.

[0005] Energy shortage is a hot issue that concerns the world. Therefore, self-powered detectors that can detect without external bias voltage have attracted widespread attention.

[0006] The self-powered solar-blind ultraviolet detectors in the prior art can be divided into two types: 1. Photovoltaic solar-blind ultraviolet detectors are obtained by heterojunctions of different materials, in which the two semiconductor materials have different bandgap widths and lattice constants; 2. Asymmetric Schottky junction type MSM type (metal-semiconductor-metal) is used, in which the metals are metals with different work functions, and form Schottky junctions with different barrier heights with the semiconductor respectively. Due to the difference in Schottky barriers, a built-in electric field is formed to form a self-powered detector, or the same metal is used, but the spatial size configuration of the two electrodes is different, resulting in the difference in the Schottky junctions on both sides to form a self-powered detector. Since these two self-powered solar-blind ultraviolet detectors use different semiconductor materials or metal materials, their preparation processes are relatively complicated, and even the preparation methods of two different semiconductor materials or metal materials may be completely different, and the cost is high; the selection of semiconductor materials and metal materials is limited, and the detector performance and detection band are difficult to adjust.

[0007] Homogeneous pn junction is the first choice for self-powered detectors. However, due to the self-compensation effect of wide bandgap semiconductor materials, the high ionization energy of acceptor impurities and other factors, it is difficult to achieve high-quality p-type materials and it is impossible to prepare homogeneous pn junctions. At present, Ga2O3 and various materials have been used to prepare heterojunction self-powered detectors, such as GaN, ZnO, SiC, MoS2, Si, etc., which are widely used in the field of solar-blind ultraviolet detection and visible-blind ultraviolet detection. x Ga 1-x )2O3 heterojunctions are rarely reported. In 2021, Wang et al. prepared (In x Ga 1-x )2O3 / Si heterojunction detector, which has self-powered detection capability in the solar-blind ultraviolet band (ACS Applied Materials & Interfaces, 2021, 13(37): 44568-44576). However, the detector has a low responsivity of only 0.48 mA / W, which needs to be further improved.

[0008] The above-mentioned heterojunction self-powered detectors use different types of semiconductor materials, which have great differences in preparation methods and processes, resulting in complex processes and difficult preparation. In addition, due to the different lattice constants of different materials, the two materials grow in layers during the growth process, resulting in poor crystal quality and easy mixing of interface elements, resulting in poor device performance.

[0009] In addition, asymmetric Schottky junctions can also be used to realize self-powered detectors. For example, (SENSORS AND ACTUATORS A-PHYSICAL, 315 (2020) 112354) a self-powered solar-blind ultraviolet detector is obtained by using Au-ZnGa2O4 Schottky junctions with asymmetric electrode spatial configuration. In addition, self-powered detectors can also be realized by using asymmetric electrodes, that is, two different electrodes (MATERIALS CHEMISTRYAND PHYSICS 166 (2015) 116).

[0010] When different metal materials are used to form an asymmetric Schottky heterojunction, due to the large bandgap width of the solar-blind ultraviolet detection material, the metal materials that can form the Schottky barrier are limited, and it is difficult to adjust the detection performance. In addition, the metal source material is expensive, and the use of different electrode materials when preparing electrodes increases the number of device preparation process steps and increases the cost. Using different spatial configurations of the same metal material to obtain an asymmetric Schottky junction self-powered solar-blind detector requires two sets of photolithography templates in the device preparation process, which not only increases the cost, but also makes the process more complicated and difficult to operate.

[0011] The above self-powered detectors mainly use Schottky-type MSM (metal-semiconductor-metal) devices, and obtain an asymmetric Schottky junction by changing the type of metal electrode material or the spatial configuration of the metal electrode, forming a built-in electric field to obtain self-powered characteristics.

[0012] For solar-blind ultraviolet detectors, the detection band is required to be less than 280nm, and the corresponding semiconductor bandgap width is required to be greater than 4.42eV. Regardless of the heterojunction of different materials or the asymmetric Schottky junction, the semiconductor materials that meet the energy band matching and the metal materials that match the work function are relatively limited. At the same time, different semiconductor materials are used to form a heterojunction, and the raw materials need to be replaced during the experiment, which is costly and complex. In addition, different semiconductor materials have different lattice constants, and there is lattice mismatch when growing materials, resulting in poor crystal quality and poor detector performance. Summary of the invention

[0013] In order to solve the technical problems in the prior art of high cost, complex process and difficulty in large-scale production of self-powered solar-blind ultraviolet detectors, the present invention provides a self-powered solar-blind ultraviolet detector with low cost, simple process and easy large-scale production and a preparation method thereof.

[0014] In order to achieve the above object, the present invention adopts the following technical solutions:

[0015] A self-powered solar-blind ultraviolet detector comprises a substrate, a film a and a film b, wherein the film a is grown on the substrate, the film b is grown on the film a, electrodes are arranged on the film a and the film b, and the film a and the film b are both (Inx Ga 1-x )2O3 material, wherein the content of In component in film a and film b materials is different.

[0016] Furthermore, the composition of film a (In x Ga 1-x The atomic ratio of In and Ga in the )2O3 material is up to 60:40at%. x Ga 1-x )The atomic ratio of In and Ga in 2O3 material is up to 30:70at%.

[0017] Furthermore, the substrate is a sapphire substrate, a silicon substrate, a quartz substrate or other substrate materials that can withstand high temperatures above 500°C.

[0018] Furthermore, the material of the electrode is capable of reacting with (In x Ga 1-x )2O3 thin film forms an ohmic contact with the metal material.

[0019] Preferably, the electrode material is Au or In, Au, Au / In alloy material or Ti / Au alloy material.

[0020] Furthermore, the thickness of the film a is 100-300 nm, and the thickness of the film b is 200-420 nm.

[0021] A method for preparing a self-powered solar-blind ultraviolet detector comprises the following steps:

[0022] Step 1: Place the substrate into the growth chamber of the magnetron sputtering equipment and select (In x Ga 1-x )2O3 target, raise the substrate temperature to 500-800℃, and grow a thin film a thereon;

[0023] Step 2: After partially shielding the film a with a mask, a layer of film b is grown on the film a at room temperature;

[0024] Step 3: evaporate electrodes on film a and film b to obtain a self-powered solar-blind ultraviolet detector.

[0025] Furthermore, in step one and step two, the target materials used are the same; the RF power of magnetron sputtering during the growth of film a and film b is 80-150W, the ratio of oxygen to argon is 4-8:30-40, and the sputtering time is 1.5-2 hours.

[0026] Furthermore, in step 1, the substrate needs to be cleaned by RCA standard cleaning method before use.

[0027] Furthermore,x Ga 1-x )The atomic ratio of In and Ga in the 2O3 target is up to 60:40at%.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (In x Ga 1-x )2O3 is an alloy material composed of Ga2O3 and In2O3. The bandgap width and lattice constant of the material can be adjusted by adjusting the content of In and Ga components. x Ga 1-x )2O3 thin films can construct heterojunctions and have self-powered detection capabilities. x Ga 1-x )2O3 heterojunction detector has its unique advantages: first, the detector design is flexible, and two suitable In concentrations (In x Ga 1-x )2O3 materials form heterojunction detectors. Secondly, different In concentrations (In x Ga 1-x )2O3 heterojunction detector has simple preparation process, easy operation and low cost.

[0030] The present invention introduces a method of using different components (In x Ga 1-x )2O3 thin film heterojunction to obtain a self-powered solar-blind ultraviolet detector. In the present invention, the different components of the stack (In x Ga 1-x )2O3 thin film heterojunction, and in the preparation process, only the growth temperature is changed, and the process parameters such as sputtering pressure, sputtering power, gas flow rate and ratio do not need to be changed to obtain different components (In x Ga 1-x )2O3 materials have different bandgap widths due to different components, thus forming a built-in electric field to obtain a self-powered detector. The process is simplified, the operation is easy, the cost is low, and the film components in the heterojunction can be changed by simply changing the growth temperature without changing the raw materials. It overcomes the shortcomings of different material heterojunctions or asymmetric Schottky junction self-powered detectors, which have complex preparation methods and high costs, and has great potential in large-scale production and practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 : Transmission spectra of film a and film b;

[0032] Figure 2: (αhν)2-hν relationship curve, where the intersection point of the curve tangent and the coordinate axis is the film bandgap width;

[0033] Figure 3 : Schematic diagram of the structure of a self-powered solar-blind ultraviolet detector;

[0034] Figure 4 :(In x Ga 1-x )2O3 heterojunction self-powered solar-blind UV detector response spectrum;

[0035] In the figure, 1, substrate; 2, film a; 3, film b; 4, electrode. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Specific implementation method 1

[0038] A self-powered solar-blind ultraviolet detector comprises a substrate 1, a film a2 and a film b3, wherein the film a2 is grown on the substrate 1, the film b3 is grown on the film a2, the film a2 and the film b3 are both provided with electrodes 4, and the film a2 and the film b3 are both (In x Ga 1-x )2O3 material, wherein the content of In component in film a2 and film b3 materials is different.

[0039] Furthermore, the composition of the film a2 (In x Ga 1-x The atomic ratio of In and Ga in the )2O3 material is up to 60:40at%. x Ga 1-x )The atomic ratio of In and Ga in 2O3 material is up to 30:70at%.

[0040] Preferably, the substrate 1 is a sapphire substrate, and other substrates may also be used, such as conventional substrates such as silicon, quartz, or other substrate materials that can withstand high temperatures above 500°C.

[0041] Furthermore, the material of the electrode 4 is capable of reacting with (In x Ga 1-x )2O3 thin film forms an ohmic contact with the metal material.

[0042] Preferably, the material of the electrode 4 is conventional electrode materials such as Au, In, Au / In alloy material or Ti / Au alloy material.

[0043] Furthermore, the thickness of the film a2 is 100-300 nm, and the thickness of the film b3 is 200-420 nm. Specific implementation method 2

[0045] A method for preparing a self-powered solar-blind ultraviolet detector according to a specific embodiment of the present invention is to prepare the detector by magnetron sputtering (In x Ga 1-x )2O3 heterojunction, specifically comprising the following steps:

[0046] Step 1: Place the substrate 1 into the growth chamber of the magnetron sputtering equipment and select (In x Ga 1-x )2O3 target, raise the substrate temperature to 500-800℃, and grow a thin film a 2 on the substrate;

[0047] Step 2: Cool to room temperature, partially cover the film a2 with a mask, and then grow a layer of film b3 on the film a2 at room temperature to obtain a stacked heterojunction structure of the film a2 and the film b3. x Ga 1-x )2O3 heterojunction growth;

[0048] Step 3: Evaporate electrode materials on film a2 and film b3 to obtain a self-powered solar-blind ultraviolet detector.

[0049] Furthermore, in step 1 and step 2, except for the growth temperature, other conditions remain unchanged and the target materials used are the same; the RF power of magnetron sputtering during the growth process of film a2 and film b3 is 80-150W, the ratio of oxygen to argon is 4-8:30-40, and the sputtering time is 1.5-2 hours.

[0050] Furthermore, in step 1, the substrate 1 needs to be cleaned by RCA standard cleaning method before use.

[0051] Furthermore, the substrate 1 is a conventional substrate such as a sapphire substrate, a silicon substrate, a quartz substrate, or other substrate materials that can withstand high temperatures above 500°C.

[0052] Furthermore, x Ga 1-x )The atomic ratio of In and Ga in the 2O3 target is up to 60:40at%.

[0053] Furthermore, the material of the electrode 4 is capable of reacting with (In x Ga 1-x)2O3 thin film forms an ohmic contact with the metal material.

[0054] Preferably, the material of the electrode 4 is Au, In, Au / In alloy material or Ti / Au alloy material.

[0055] In the detector, due to different growth temperatures, film a2 and film b3 have different contents of In components, thus having different bandgap widths, generating a built-in electric field to obtain a self-powered detector. The preparation method is simple and easy to operate, low in cost, easy to implement and easy to promote.

[0056] In order to verify that different growth temperatures will lead to different contents of In components in film a2 and film b3, thus leading to different band gaps, the absorption spectra of the films grown at different temperatures were measured, and the optical band gaps of the films were calculated based on the absorption spectra, as shown in Figure 2. Figure 1 and Figure 2 The structural schematic diagram of the self-powered solar-blind ultraviolet detector of the present invention is shown in Figure 3 As shown, the performance of the detector is Figure 4 shown.

[0057] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A self-powered solar-blind ultraviolet detector, characterized in that: The invention comprises a substrate, a film a and a film b, wherein the film a is grown on the substrate, the film b is grown on the film a, electrodes are arranged on the film a and the film b, and the film a and the film b are both (In x Ga 1-x )2O3 material, wherein the content of In component in film a and film b materials is different.

2. A self-powered solar-blind ultraviolet detector according to claim 1, characterized in that: Composition of film a (In x Ga 1-x The atomic ratio of In and Ga in the )2O3 material is up to 60:40at%. x Ga 1-x )The atomic ratio of In and Ga in 2O3 material is up to 30:70at%.

3. A self-powered solar-blind ultraviolet detector according to claim 1, characterized in that: The substrate is a sapphire substrate, a silicon substrate, a quartz substrate or other substrate materials that can withstand high temperatures above 500°C.

4. A self-powered solar-blind ultraviolet detector according to claim 1, characterized in that: The material of the electrode is x Ga 1-x )2O3 thin film forms an ohmic contact with the metal material.

5. A self-powered solar-blind ultraviolet detector according to claim 4, characterized in that: The electrode material is Au or In, Au, Au / In alloy material or Ti / Au alloy material.

6. A self-powered solar-blind ultraviolet detector according to claim 1, characterized in that: The thickness of the film a is 100-300 nm, and the thickness of the film b is 200-420 nm.

7. A method for preparing a self-powered solar-blind ultraviolet detector, characterized in that: The following steps are involved: Step 1: Place the substrate into the growth chamber of the magnetron sputtering equipment and select (In x Ga 1-x )2O3 target, raise the substrate temperature to 500-800℃, and grow a thin film a thereon; Step 2: After partially shielding the film a with a mask, a layer of film b is grown on the film a at room temperature; Step 3: evaporate electrodes on film a and film b to obtain a self-powered solar-blind ultraviolet detector.

8. The method for preparing a self-powered solar-blind ultraviolet detector according to claim 7, characterized in that: In step 1 and step 2, the target materials used are the same; during the growth process of film a and film b, the RF power of magnetron sputtering is 80-150W, the ratio of oxygen to argon is 4-8:30-40, and the sputtering time is 1.5-2 hours.

9. The method for preparing a self-powered solar-blind ultraviolet detector according to claim 7, characterized in that: In step 1, the substrate needs to be cleaned by RCA standard cleaning method before use.

10. The method for preparing a self-powered solar-blind ultraviolet detector according to claim 7, characterized in that: (In x Ga 1-x )The atomic ratio of In and Ga in the 2O3 target is up to 60:40at%.

Images