Photoconductive device and infrared detector

Abstract

The invention provides a preparation method of a photoconductive device and an infrared detector, and the preparation method of the photoconductive device comprises the steps: mixing a lead source precursor solution and a selenium source precursor solution, and adding a metal iodide salt for sensitization at the same time, thereby obtaining a lead selenide solution; growing a lead selenide film on a substrate by using the lead selenide solution; and arranging an electrode on the lead selenide thin film to prepare the photoconductive device. According to the method, the chemical bath deposition technology is used for preparing the lead selenide thin film, an aqueous solution of metal iodide salt is added in situ in the thin film growth process, the induction period of growth of the lead selenide thin film is prolonged, lead selenide crystal grains are arranged more compactly, internal defects of the thin film are reduced, and the doping concentration is remarkably reduced. According to the in-situ sensitization strategy, the grain boundary potential barrier is reduced, grain boundary recombination is reduced, the dark current is reduced, and the light response is remarkably improved.

Description

Technical Field

[0001] The present application relates to the technical field of electronic materials, and in particular to a photoconductive device and an infrared detector. Background Art

[0002] Lead selenide is an important narrow bandgap semiconductor material for infrared detection. It has a direct bandgap with a bandgap width of 0.27 eV at 300K, so its intrinsic absorption cutoff wavelength at room temperature can reach 4.5μm. The Auger recombination coefficient of lead selenide is 1 to 2 orders of magnitude lower than that of other semiconductors with similar bandgaps. Its Auger recombination is actually dominated by an indirect recombination process assisted by phonons and is less affected by temperature. Therefore, it can work at room temperature and does not require a refrigeration system, reducing preparation costs. These properties make lead selenide semiconductor films very popular in the field of mid-wave infrared detection, and they can be widely used in astronomy, earth sciences, industrial gas monitoring, and military fields.

[0003] Traditional lead selenide detectors are mainly photoconductive structures, and chemical water bath deposition technology is a common preparation method. The obtained lead selenide film usually needs sensitization treatment to activate the infrared light response. Unsensitized lead selenide film is difficult to have infrared response. At present, the sensitization of lead selenide film basically includes two steps: high-temperature oxidation and iodination. That is, oxygen and iodine vapor are introduced into a vacuum tube furnace in a high-temperature atmosphere to react with the lead selenide film, changing the elemental composition and atomic distribution on the surface of the lead selenide film. However, this high-temperature process will have a destructive effect on the readout circuit of the imaging array, affecting the performance of the device.

[0004] Application Contents

[0005] In view of the above problems, the present application provides a photoconductive device and an infrared detector for improving device performance, specifically reducing dark current and significantly improving light response; and the preparation process is simple, easy to control, and low-cost.

[0006] In a first aspect, a method for preparing a photoconductive device is provided, comprising:

[0007] preparing a lead source precursor solution and a selenium source precursor solution;

[0008] The lead source precursor solution and the selenium source precursor solution are mixed, and a metal iodide salt is added for sensitization to obtain a lead selenide solution;

[0009] growing a lead selenide thin film on a substrate using the lead selenide solution;

[0010] An electrode is arranged on the lead selenide film to prepare a photoconductive device.

[0011] Wherein, preparing the lead source precursor solution comprises:

[0012] Adding sodium citrate to an aqueous solution containing a lead source, and filtering to obtain the lead source precursor solution;

[0013] Wherein, the aqueous solution containing the lead source includes at least one of lead nitrate and lead acetate.

[0014] Wherein, the concentration of the aqueous solution containing the lead source is 0.01mM to 0.015mM;

[0015] The content of the sodium citrate is 0.1 mM to 0.15 mM.

[0016] Wherein, preparing the selenium source precursor solution comprises:

[0017] Sodium sulfite is added to an aqueous solution containing a selenium source, and the selenium source precursor solution is obtained after filtering; wherein the aqueous solution containing a selenium source includes at least one of selenourea and N'N-dimethylselenourea.

[0018] Wherein, the concentration of the aqueous solution containing the selenium source is 0.01mM to 0.015mM;

[0019] The content of the sodium sulfite is 0.025mM to 0.075mM.

[0020] Wherein, the molar ratio of the lead source precursor solution to the selenium source precursor solution is 1:1.

[0021] Wherein, the metal iodide salt includes at least one of ammonium iodide, sodium iodide, potassium iodide, rubidium iodide, cesium iodide, chromium iodide, zinc iodide, and lead iodide;

[0022] The concentration of the metal iodide salt is 0.005-0.01 mM, and the content of the metal iodide salt is 5×10 -7 ~1×10 -6 mmol.

[0023] Wherein, using the lead selenide solution to grow a lead selenide film on a substrate comprises:

[0024] Pre-treating the substrate;

[0025] placing the pretreated substrate into the lead selenide solution for growth to obtain a lead selenide film;

[0026] Wherein, the lead selenide film has a thickness of 500nm to 1000nm;

[0027] The pretreatment includes: cleaning the substrate and performing thermal evaporation on the cleaned substrate to evaporate the lead selenide seed layer.

[0028] Wherein, an electrode is arranged on the lead selenide film to prepare a photoconductive device, comprising:

[0029] Using a thermal evaporation method, evaporating a metal conductive layer at both ends of the lead selenide film as the electrode, thereby obtaining the photoconductive device;

[0030] Wherein, the material of the metal conductive layer is gold.

[0031] In a second aspect, the present application provides an infrared detector, which includes a photoconductive device prepared by any of the methods described above.

[0032] The technical solution provided in the embodiment of the present application is to add a metal iodide salt to sensitize the mixture of the lead source precursor solution and the selenium source precursor solution, thereby obtaining a lead selenide solution; using the lead selenide solution to grow a lead selenide film on a substrate; and setting electrodes on the lead selenide film to prepare a photoconductive device. The method uses a chemical bath deposition technique to prepare a lead selenide film, and in situ adds an aqueous solution of a metal iodide salt during the film growth process, which prolongs the induction period of the lead selenide film growth, makes the lead selenide grain arrangement more dense, reduces the internal defects of the film, and significantly reduces the doping concentration. The in-situ sensitization strategy reduces the grain boundary barrier, reduces grain boundary recombination, reduces the dark current, and significantly improves the light response.

[0033] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0035] Figure 1 It is a schematic flow chart of an embodiment of a method for preparing a photoconductive device of the present application;

[0036] Figure 2 It is a structural schematic diagram of an embodiment of the infrared detector of the present application. DETAILED DESCRIPTION

[0037] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0038] Various structural schematic diagrams according to embodiments of the present disclosure are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may further design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0039] Traditional lead selenide detectors are mainly photoconductive structures, and chemical water bath deposition technology is a common preparation method. The obtained lead selenide film usually needs sensitization treatment to activate the infrared light response. Unsensitized lead selenide film is difficult to have infrared response. At present, the sensitization of lead selenide film basically includes two steps: high-temperature oxidation and iodination. That is, oxygen and iodine vapor are introduced into a vacuum tube furnace in a high-temperature atmosphere to react with the lead selenide film, changing the elemental composition and atomic distribution on the surface of the lead selenide film. However, this high-temperature process will have a destructive effect on the readout circuit of the imaging array.

[0040] The present application provides a method for preparing a photoconductive device and an infrared detector. The method for preparing the photoconductive device can be implemented in a low-temperature environment. The method for preparing a photoconductive device comprises: preparing a lead source precursor solution and a selenium source precursor solution; mixing the lead source precursor solution and the selenium source precursor solution, and adding a metal iodide salt for sensitization, thereby obtaining a lead selenide solution; growing a lead selenide film on a substrate using the lead selenide solution; and setting electrodes on the lead selenide film, thereby preparing a photoconductive device. This method abandons the traditional high-temperature sensitization strategy, and directly sensitizes the lead selenide film during the growth of the film to make it light-responsive. The resulting lead selenide film has dense grain arrangement and has a medium-wave infrared light response. The entire preparation process is simple and easy to control, the preparation device is simple, and the cost is low.

[0041] The present application will be described in detail below with reference to the accompanying drawings.

[0042] See also Figure 1 , Figure 1 1 is a schematic flow chart of a first embodiment of a method for preparing a photoconductive device of the present application, which specifically includes:

[0043] Step S11: preparing a lead source precursor solution and a selenium source precursor solution.

[0044] In this step, the lead source precursor solution is prepared, including: adding sodium citrate to an aqueous solution containing a lead source, filtering to obtain the lead source precursor solution; wherein the aqueous solution containing the lead source includes at least one of lead nitrate and lead acetate. The concentration of the aqueous solution containing the lead source is 0.01mM to 0.015mM; and the content of the sodium citrate is 0.1mM to 0.15mM.

[0045] In this step, preparing a selenium source precursor solution includes: adding sodium sulfite to an aqueous solution containing a selenium source, filtering and obtaining the selenium source precursor solution; wherein the aqueous solution containing a selenium source includes at least one of selenourea and N'N-dimethylselenourea. The concentration of the aqueous solution containing a selenium source is 0.01mM to 0.015mM; and the content of the sodium sulfite is 0.025mM to 0.075mM.

[0046] Step S12: mixing the lead source precursor solution and the selenium source precursor solution, and adding a metal iodide salt for sensitization, thereby obtaining a lead selenide solution.

[0047] Specifically, the lead source precursor solution A and the selenium source precursor solution B are mixed and 100 μL of 25% to 28% wt ammonia water is added, and then a small amount of aqueous solution of metal iodide salt is added for sensitization to obtain a lead selenide solution. The molar ratio of the lead source precursor solution to the selenium source precursor solution is 1:1.

[0048] In one embodiment, the metal iodide salt includes at least one of ammonium iodide, sodium iodide, potassium iodide, rubidium iodide, cesium iodide, chromium iodide, zinc iodide, and lead iodide; the concentration of the metal iodide salt is 0.005-0.01 mM, and the content of the metal iodide salt is 5×10 -7 ~1×10 -6 mmol.

[0049] Step S13: growing a lead selenide thin film on a substrate using the lead selenide solution.

[0050] Specifically, the substrate is pretreated; the pretreatment includes: cleaning the substrate and performing thermal evaporation on the cleaned substrate to evaporate the lead selenide seed layer.

[0051] In one embodiment, cleaning the substrate comprises: ultrasonic cleaning with detergent, deionized water, acetone, isopropanol, and ethanol for 20 minutes each, and after drying, placing the substrate in an ultraviolet ozone or plasma cleaning machine for 5-10 minutes for standby use.

[0052] In one embodiment, when thermal evaporation is performed on the cleaned substrate to form a lead selenide seed layer, the evaporation current of the thermal evaporation is 70A and the evaporation pressure is <10 -4 Pa, the thermal evaporation is carried out in a thermal evaporation chamber, and the lead selenide powder is evaporated onto the substrate by thermal evaporation, and the evaporation thickness is 1nm to 5nm.

[0053] The pretreated substrate is placed in the lead selenide solution for growth to obtain a lead selenide film. Optionally, the growth temperature is 25° C., the growth time is 6 hours, and the thickness of the obtained lead selenide film is 500 nm to 1000 nm.

[0054] Step S14: Arranging electrodes on the lead selenide film to prepare a photoconductive device.

[0055] In one embodiment, a metal conductive layer is evaporated at both ends of the lead selenide film as the electrode by thermal evaporation to obtain the photoconductive device; wherein the metal conductive layer material is gold. In this process, the evaporation current of thermal evaporation is 100A to 130A, and the evaporation pressure is <10 -4 Pa; the thermal evaporation is performed in a thermal evaporation chamber, and the gold particles are evaporated onto the substrate by thermal evaporation. The thickness of the metal conductive layer is 80nm.

[0056] The time-resolved photoresponse diagram of the photoconductive detector prepared by adding a lead selenide thin film grown with a metal iodide salt under 2.1 μm laser irradiation and 1 V bias voltage shows that the device has good repeatable switching performance, and the dark current of the device is measured to be 403 nA and the photocurrent is 502 nA.

[0057] The preparation method of the photoconductive device proposed in the present invention has a simple process and low cost. It abandons the traditional high-temperature sensitization strategy of annealing in a tubular furnace atmosphere, solves the problems of many internal defects, high doping concentration, disordered grain stacking, and weak infrared light response of the current chemical liquid phase deposited lead selenide film, and is convenient for integration with the readout circuit of the imaging array to prepare a high-performance lead selenide infrared detection chip. Specifically, the lead selenide film is prepared using a chemical bath deposition technique, and an aqueous solution of a metal iodide salt is added in situ during the film growth process, which prolongs the induction period of the lead selenide film growth, makes the lead selenide grain arrangement more dense, reduces the internal defects of the film, and significantly reduces the doping concentration. The in-situ sensitization strategy reduces the grain boundary barrier and grain boundary recombination, reduces the dark current, and significantly improves the light response.

[0058] See also Figure 2, is a schematic diagram of the structure of an embodiment of the infrared detector of the present application. In this embodiment, the infrared detector 10 includes a photoconductive device 20, and the photoconductive device 20 is prepared by the method described in the above embodiment. The photoconductive device 20 is applied to the infrared detector 10, so that the infrared detector 10 has the characteristics of reduced dark current and significantly improved light response.

[0059] The algorithm and display provided herein are not inherently related to any particular computer, virtual system or other device. Various general purpose systems can also be used together with the teachings based on this. According to the above description, it is obvious that the structure required for constructing such systems. In addition, the application is not directed to any specific programming language either. It should be understood that various programming languages ​​can be utilized to realize the content of the application described herein, and the description of the specific language above is for the purpose of disclosing the best mode of implementation of the application.

[0060] In the description provided herein, a large number of specific details are described. However, it is understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0061] Similarly, it should be understood that in order to streamline the present disclosure and assist in understanding one or more of the various aspects of the application, in the above description of exemplary embodiments of the present application, the various features of the present application are sometimes grouped together into a single embodiment, figure, or description thereof.

[0062] Those skilled in the art will appreciate that the modules in the device in the embodiment can be adaptively changed and arranged in one or more devices different from the embodiment. The modules or units or components in the embodiment can be combined into one module or unit or component, and in addition they can be divided into multiple submodules or subunits or subcomponents. Except that at least some of such features and / or processes or units are mutually exclusive, all features disclosed in this specification (including abstracts and drawings) and all processes or units of any method or device disclosed in this manner can be combined in any combination. Unless otherwise explicitly stated, each feature disclosed in this specification (including accompanying abstracts and drawings) can be replaced by alternative features that provide the same, equivalent or similar purposes.

[0063] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not other features, the combination of features from different embodiments is meant to be within the scope of the present application and to form different embodiments.

[0064] It should be noted that the above embodiments illustrate the present application rather than limit the present application. Any reference symbol between brackets should not be constructed as a limitation to the present application. The word "comprising" does not exclude the existence of components or steps not listed in the present application. The word "one" or "an" before a component does not exclude the existence of multiple such components. The present application can be implemented by means of hardware including several different components and by means of a suitably programmed computer. In the embodiments in which several devices are listed, several of these devices can be embodied by the same hardware item. The use of the words first, second, and third, etc. does not indicate any order. These words can be interpreted as names.

Claims

1. A method for preparing a photoconductive device, characterized in that: include: preparing a lead source precursor solution and a selenium source precursor solution; The lead source precursor solution and the selenium source precursor solution are mixed, and a metal iodide salt is added for sensitization to obtain a lead selenide solution; growing a lead selenide thin film on a substrate using the lead selenide solution; An electrode is arranged on the lead selenide film to prepare a photoconductive device.

2. The preparation method according to claim 1, characterized in that: Prepare a lead source precursor solution, including: Adding sodium citrate to an aqueous solution containing a lead source, and filtering to obtain the lead source precursor solution; Wherein, the aqueous solution containing the lead source includes at least one of lead nitrate and lead acetate.

3. The preparation method according to claim 2, characterized in that: The concentration of the aqueous solution containing the lead source is 0.01 mM to 0.015 mM; The content of the sodium citrate is 0.1 mM to 0.15 mM.

4. The preparation method according to claim 1, characterized in that: Prepare a selenium source precursor solution, including: Sodium sulfite is added to an aqueous solution containing a selenium source, and the selenium source precursor solution is obtained after filtering; wherein the aqueous solution containing a selenium source includes at least one of selenourea and N'N-dimethylselenourea.

5. The preparation method according to claim 4, characterized in that: The concentration of the aqueous solution containing the selenium source is 0.01mM to 0.015mM; The content of the sodium sulfite is 0.025mM to 0.075mM.

6. The preparation method according to claim 1, characterized in that: The molar ratio of the lead source precursor solution to the selenium source precursor solution is 1:

1.

7. The preparation method according to claim 1, characterized in that: The metal iodide salt includes at least one of ammonium iodide, sodium iodide, potassium iodide, rubidium iodide, cesium iodide, chromium iodide, zinc iodide, and lead iodide; The concentration of the metal iodide salt is 0.005-0.01 mM, and the content of the metal iodide salt is 5×10 -7 ~1×10 -6 mmol.

8. The preparation method according to claim 1, characterized in that: The lead selenide solution is used to grow a lead selenide film on a substrate, comprising: Pre-treating the substrate; placing the pretreated substrate into the lead selenide solution for growth to obtain a lead selenide film; Wherein, the lead selenide film has a thickness of 500nm to 1000nm; The pretreatment includes: cleaning the substrate and performing thermal evaporation on the cleaned substrate to evaporate the lead selenide seed layer.

9. The preparation method according to claim 1, characterized in that: An electrode is arranged on the lead selenide film to prepare a photoconductive device, comprising: Using a thermal evaporation method, evaporating a metal conductive layer at both ends of the lead selenide film as the electrode, thereby obtaining the photoconductive device; Wherein, the material of the metal conductive layer is gold.

10. An infrared detector, characterized in that: The infrared detector comprises a photoconductive device prepared by the method according to any one of claims 1 to 9 above.

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