Preparation method and application of quantum dot sensitized silicon-based double Schottky junction near-infrared detector

Abstract

The invention discloses a near-infrared photoelectric detector based on quantum dot sensitized silicon-based double Schottky junctions and a preparation method of the near-infrared photoelectric detector, and solves the problems of low quantum efficiency, high material toxicity and poor process compatibility of a traditional detector in a 1050nm waveband. According to the detector, silver chalcogenide quantum dots are used as a sensitization layer, the sensitization layer is coupled with a monocrystalline silicon substrate through a spin-coating process, and after interface characteristics are optimized through ligand exchange, metal electrodes are sequentially evaporated to construct a double Schottky heterojunction. According to the invention, a charge transfer channel on silicon is constructed by using a novel quantum dot material, the photoelectric responsivity of a silicon device in a near-infrared band is greatly improved, and zero-bias near-infrared self-powered detection is realized by using the difference between junctions of a double Schottky junction structure. Compared with a conventional near-infrared detection scheme, the near-infrared detector has the advantages of no toxicity, miniaturization, low cost, compatibility with a silicon-based chip process and the like, the responsivity is improved by about one order of magnitude compared with a traditional indium gallium arsenic detector, and the near-infrared detector has application potential in the fields of biological imaging, optical communication and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric detectors, and in particular relates to a low-cost, non-toxic, quantum dot-sensitized silicon-based double Schottky junction near-infrared detector, and a preparation method and application thereof. Background Art

[0002] Due to its excellent penetrating ability, near-infrared light (NIR) plays a vital role in many fields such as imaging, optical communication systems, biomedical instruments, environmental monitoring, and machine vision. Traditional near-infrared photodetectors usually use epitaxially grown narrow-bandgap semiconductor materials such as mercury cadmium telluride, indium gallium arsenide, and indium cadmium telluride. However, the growth of these materials requires extremely high temperatures and vacuum levels, resulting in high process costs. Secondly, due to lattice matching requirements, these materials are usually only suitable for specific substrates, and complex flip-chip bonding technology is required when integrating with silicon-based circuits and chips. In addition, some detectors also need to be combined with complex temperature control devices, making miniaturization difficult. For the above reasons, the application of traditional near-infrared semiconductor materials is greatly limited.

[0003] Currently, silicon-based single-photon avalanche detectors (SPDs), such as the STMicroelectronics VL53L5CX, can detect near-infrared light from 850nm to 1050nm. However, due to silicon's inherent bandgap characteristics, their external quantum efficiency at 1050nm is low, requiring high-power light sources to compensate. Indium gallium arsenide (InGaAs) detectors, such as the Hamamatsu G12180-204A, can detect light over a wide range of near-infrared light, achieving an external quantum efficiency of 80% at 1050nm. However, their high cost and cryogenic operation (-20°C) make them difficult to commercialize on a large scale. Silicon-germanium avalanche photodetectors, such as the ON Semiconductor MicroFC-60035-SMT, can extend the detection band to 1050nm through silicon doping while achieving high gain. However, their fabrication process involves specialized processes such as deep-well doping and backside thinning, resulting in complex and costly manufacturing and hindering large-scale commercialization. Summary of the Invention

[0004] The main purpose of the present invention is to significantly improve the photoelectric detection capability of silicon-based materials in the near-infrared band by sensitizing silicon-based materials with quantum dots and constructing a double Schottky junction device structure, thereby overcoming the shortcomings of the existing technology.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a quantum dot-sensitized silicon-based double Schottky junction near-infrared detector, comprising the following steps:

[0006] (1) Weighing an appropriate amount of narrow-bandgap quantum dot powder, dispersing it in an organic non-polar solvent, and ultrasonically treating it to form a uniform quantum dot solution;

[0007] (2) taking a small amount of the quantum dot solution obtained in step (1), uniformly coating the surface of the cleaned single crystal silicon wafer, and then immersing it in the short chain ligand solution after drying, and then drying it on a hot plate, and performing multiple rounds of "coating-drying-immersion-drying" cycles;

[0008] (3) The single crystal silicon wafer coated with quantum dots after recycling is processed into a metal electrode using a mask to produce a double Schottky junction device with self-powered photodetection function.

[0009] Furthermore, in step (1), the narrow bandgap quantum dots are any one or more combinations of silver sulfide quantum dots, lead sulfide quantum dots, mercury sulfide quantum dots, and ternary quantum dots derived therefrom.

[0010] Furthermore, in step (1), the organic non-polar solvent is any one or more combinations of cyclohexane and chloroform.

[0011] Furthermore, in step (2), the uniform coating process includes various coating methods such as spin coating, drop coating, spray coating, dip coating or Meyer rod coating.

[0012] Furthermore, in step (2), the short-chain ligand is an acetonitrile solution of any one or more combinations of ethanedithiol, butanethiol, and n-octanethiol, and a similar charge transfer enhancement effect can be achieved when the carbon chain length is ≤C8, which can be specifically optimized and selected through routine experiments.

[0013] Furthermore, in step (3), the metal electrode needs to satisfy the matching of its work function with the energy level of the quantum dots to construct a Schottky contact.

[0014] Furthermore, in step (3), the dual Schottky junction device is composed of two back-to-back Schottky junctions, and realizes a self-powered photoelectric detection function through a built-in electric field.

[0015] Another aspect of the present invention provides a quantum dot-sensitized silicon-based double Schottky junction near-infrared detector prepared by the above-mentioned preparation method, comprising: a single crystal silicon substrate; a narrow bandgap quantum dot sensitization layer coated on the surface of the single crystal silicon substrate, the quantum dot sensitization layer being modified with short-chain ligands to achieve gradient energy band matching with the silicon substrate; two back-to-back metal electrodes forming Schottky contacts with the quantum dot sensitization layer respectively to form a double Schottky junction structure; the double Schottky junction achieves self-powered near-infrared light detection under zero bias through a built-in electric field.

[0016] Another aspect of the present invention provides an application of the above-mentioned quantum dot-sensitized silicon-based double Schottky junction near-infrared detector in a silicon-based device integrated system.

[0017] The beneficial technical effects of the present invention are embodied in the following aspects:

[0018] This paper proposes, for the first time, the construction of a narrow-bandgap quantum dot-sensitized double Schottky junction structure on a single-crystal silicon surface, breaking through the existing research paradigm, which is limited to quantum dot-sensitized solar cells (QDSSCs) or single Schottky junction detectors. This back-to-back double Schottky junction structure, through the synergistic effect of the built-in electric field, theoretically enables more efficient separation of photogenerated carriers, successfully achieving self-powered detection.

[0019] The use of narrow-bandgap quantum dot materials and a silicon substrate to form a gradient energy band matching structure, combined with a short-chain ligand surface modification process, significantly improves the interfacial charge transfer efficiency. This gradient energy level design enables the device to achieve an optical absorption coefficient at 1050nm that is 50 times that of traditional silicon devices.

[0020] Through the spin coating-annealing cycle process of quantum dot solution and immersion treatment in short-chain ligand (such as thiol) solution, the quantum dot layer is self-assembled layer by layer on the silicon wafer surface to form a dense sensitization layer with controllable thickness and low defect density.

[0021] Compared to traditional near-infrared detectors, this solution offers advantages such as non-toxicity, miniaturization, low cost, and the absence of an additional temperature control system. Its measured responsivity is approximately an order of magnitude higher than that of traditional InGaAs detectors. Examples demonstrate that the dual Schottky junction device's near-infrared responsivity at 1050nm is approximately 50 times higher than that of silicon. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a TEM image of the silver telluride quantum dots synthesized in Example 1;

[0023] Figure 2 is a structural diagram of the device prepared in Example 1;

[0024] Figure 3 This is a physical diagram of the device in Example 1;

[0025] Figure 4 is a response curve of the device in Example 1 to 1050nm near-infrared light;

[0026] Figure 5 is the energy band relationship diagram of each material in Example 1;

[0027] Figure 6 This is the self-powered light response phenomenon brought about by the back-facing double Schottky junction structure of the device in Example 1;

[0028] Figure 7This is a structural diagram of the device prepared in Comparative Example 1;

[0029] Figure 8 is a graph showing the response of the device in Comparative Example 1 to 1050nm near-infrared light;

[0030] Figure 9 This is a structural diagram of the device prepared in Comparative Example 2;

[0031] Figure 10 This is a response curve of the device in Comparative Example 2 to 1050nm near-infrared light. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0033] Example 1

[0034] Preparation of dual Schottky devices of silver telluride quantum dots sensitized silicon:

[0035] (1) In a glove box, 0.05-0.2 g of a silver source and 10-50 mL of dodecanethiol were weighed and directly mixed in a reaction vessel, and 0.5-5 g of tellurium powder was weighed and dissolved in 5-50 mL of tributylphosphine to prepare a tellurium precursor; the reaction precursor was preheated under magnetic stirring;

[0036] (2) heating the reaction mixture at a rate of 5-10°C / min. When the temperature reaches 80-120°C and stabilizes, rapidly injecting 0.1-10 mL of a tellurium precursor and maintaining the mixture for 5-30 minutes. After the reaction, remove the heat source from the solution and allow it to cool naturally to room temperature.

[0037] (3) After removing the reactant precipitate, acetone is added to the supernatant for centrifugal separation, and the supernatant is removed to obtain a black precipitate. The precipitate product is collected and stored in a glove box. When used, a certain amount of the product is dispersed in cyclohexane to obtain a silver telluride quantum dot solution;

[0038] (4) Take 10-100 μL of quantum dot solution and evenly disperse it on the cleaned single crystal silicon wafer by spin coating at 800-2000 rpm for 10-100 seconds. After drying, soak it in 1-20 mM ethanedithiol acetonitrile solution for 3-5 seconds for ligand exchange. After drying again, spin coating the next layer of quantum dot film. Repeat the spin coating and soaking process multiple times.

[0039] (5) The silicon wafer coated with quantum dots and after ligand exchange is processed into aluminum electrodes using a mask to construct a double Schottky junction device.

[0040] The device prepared in Example 1 was tested, and the results are shown in Figures 1 to 7.

[0041] Figure 1 This is a TEM image of silver telluride quantum dots prepared under the conditions of Example 1 of the present invention. It can be seen that the prepared quantum dots have uniform size distribution and no obvious agglomeration occurs.

[0042] Figure 2 This is a structural diagram of the prepared device, with metallic aluminum covering the quantum dot layer.

[0043] Figure 3 This is a physical picture of the prepared device. The response area (A) of this device is 3×10 -4 cm 2 , and all subsequent comparative examples are based on this response area.

[0044] Figure 4 The device made by the present invention is 0.2mW / cm 2 The black line is the volt-ampere curve of the device under 1050nm light. The dark current (I Dark ) is 0.9×10 -6 A, the gray line is when the power (P) is 0.2mW / cm 2 The voltammetric curve under 1050nm light irradiation, the photocurrent at 1.5V (I Lig h t ) is 9.9×10 -6 A, according to the response calculation formula The device has a responsivity of 150A / W at a working voltage of 1.5V. q is the unit charge, and the device has a specific detection rate of 4.8×10 12 Jones.

[0045] Figure 5 This is a diagram of the energy band relationship of the device in Example 1 of the present invention. In terms of the selection of electrode metals, a Schottky junction is formed between the silver telluride quantum dots and the aluminum electrode, so that the device consists of two opposite Schottky junctions;

[0046] Figure 6 The device in Example 1 of the present invention is subjected to a periodic exposure of 0.2 mW / cm2 at zero bias. 2 The response curve under 1050nm light irradiation shows a slight asymmetry due to the statistical difference of the aluminum-quantum point contact in the back-to-back double Schottky junction, which leads to self-powered phenomenon under zero bias. At this time, the device responsivity is 1.03A / W and the specific detectivity is 5.6×10 12 Jones.

[0047] Comparative Example 1

[0048] Preparation of silver telluride quantum dot silicon-based photoconductive devices:

[0049] (1) Weighing 0.05-0.2 g of silver source and 10-50 mL of dodecanethiol and then directly mixing them in a reaction vessel, and weighing 0.5-5 g of tellurium powder and dissolving them in 5-50 mL of tributylphosphine to prepare a tellurium precursor; preheating the reaction vessel in a magnetic stirrer, and replacing the air in the reaction vessel with a nitrogen environment using a vacuum pump;

[0050] (2) heating the reaction mixture at a rate of 5-10°C / min. When the temperature reaches 80-120°C and stabilizes, rapidly inject 0.1-10 mL of a tellurium precursor and store for 5-30 minutes. After the reaction, remove the heat source from the solution and allow it to cool naturally to room temperature.

[0051] (3) After removing the reactant precipitate, acetone is added to the supernatant for centrifugal separation, and the supernatant is removed to obtain a black precipitate. The precipitate is washed multiple times and then dispersed in cyclohexane to obtain a silver telluride quantum dot solution;

[0052] (4) Using a mask to evaporate aluminum electrodes on clean single crystal silicon;

[0053] (5) Take 10-100 μL of quantum dot solution and evenly disperse it on the single crystal silicon wafer coated with electrode by spin coating at 800-2000 rpm for 10-100 s. After drying, soak it in 1-20 mM ethanedithiol acetonitrile solution, and repeat the dispersion and soaking process multiple times;

[0054] The device prepared in Comparative Example 1 was tested, and the results are shown in Figures 7 and 8.

[0055] Figure 7 This is a structural diagram of the prepared device, in which the quantum dot layer is covered on metallic aluminum.

[0056] Figure 8 The device prepared in Example 1 is 0.2mW / cm 2 The black line is the volt-ampere curve of the device under 1050nm light. The dark current (I Dark ) is 0.01×10 -6 A, the gray line is when the power (P) is 0.2mW / cm 2 The voltammetric curve under 1050nm light irradiation, the photocurrent at 1.5V (I Light ) is 0.32×10 -6 A, according to the response calculation formula The device has a responsivity of 5.2A / W at an operating voltage of 1.5V and a specific detectivity of 1.6×10 12 Jones, the device responsivity in Example 1 of the present invention is about 30 times that of the comparative example.

[0057] Comparative Example 2

[0058] Silicon-aluminum contact device preparation:

[0059] (1) Using a mask to evaporate aluminum electrodes on clean single-crystal silicon to obtain a silicon-aluminum contact type detection device;

[0060] The test results of the device of Comparative Example 2 are shown in Figures 9 and 10.

[0061] Figure 9 3 is a structural diagram of the prepared device, in which the aluminum electrode is directly evaporated on the same single crystal silicon wafer as in Example 1 and Comparative Example 1.

[0062] Figure 10 The device of Example 2 is at 0.2mW / cm 2 The black line is the volt-ampere curve of the device under 1050nm light. The dark current (I Dark ) is 0.007×10 -6 A, the gray line is when the power (P) is 0.2mW / cm 2 The voltammetric curve under 1050nm light irradiation, the photocurrent at 1.5V (I Light ) is 0.201×10 -6 A, according to the response calculation formula The device has a responsivity of 3.2A / W at an operating voltage of 1.5V and a specific detectivity of 1.17×10 12 Jones, the device responsivity in Example 1 of the present invention is about 50 times that of the comparative example.

Claims

1. A method for preparing a quantum dot-sensitized silicon-based double Schottky junction near-infrared detector, characterized in that: The following steps are involved: (1) In a glove box, all subsequent operations were performed in the glove box. An appropriate amount of narrow-bandgap quantum dot powder was weighed, dispersed in an organic non-polar solvent, and ultrasonically treated to form a uniform quantum dot solution. (2) taking a small amount of the quantum dot solution obtained in step (1), uniformly coating it on the surface of the cleaned single crystal silicon wafer, and then immersing it in the short chain ligand solution after drying, and then drying it on a hot plate, and then performing multiple rounds of "coating-drying-immersion-drying" cycles; (3) The single crystal silicon wafer coated with quantum dots after recycling is processed into a metal electrode using a mask to produce a double Schottky junction device with self-powered photodetection function.

2. The method for preparing a quantum dot-sensitized silicon-based double Schottky junction near-infrared detector according to claim 1, characterized in that: In step (1), the narrow bandgap quantum dots are any one or more combinations of silver sulfide quantum dots, lead sulfide quantum dots, mercury sulfide quantum dots, and ternary quantum dots derived therefrom.

3. The method for preparing a quantum dot-sensitized silicon-based double Schottky junction near-infrared detector according to claim 1, characterized in that: In step (1), the organic non-polar solvent is any one or more combinations of cyclohexane and chloroform.

4. The method for preparing a quantum dot-sensitized silicon-based double Schottky junction near-infrared detector according to claim 1, wherein: In step (2), the uniform coating process includes various coating methods such as spin coating, drop coating, spray coating, dip coating or Meyer rod coating.

5. The method for preparing a quantum dot-sensitized silicon-based double Schottky junction near-infrared detector according to claim 1, wherein: In step (2), the short-chain ligand is an acetonitrile solution of any one or more combinations of ethanedithiol, butanethiol, and n-octanethiol.

6. The method for preparing a quantum dot-sensitized silicon-based double Schottky junction near-infrared detector according to claim 1, wherein: In step (3), the metal electrode must satisfy the matching of its work function with the energy level of the quantum dots to construct a Schottky contact.

7. The method for preparing a quantum dot-sensitized silicon-based double Schottky junction near-infrared detector according to claim 1, characterized in that: In step (3), the dual Schottky junction device is composed of two back-to-back Schottky junctions, and realizes a self-powered photoelectric detection function through a built-in electric field.

8. A quantum dot-sensitized silicon-based double Schottky junction near-infrared detector prepared by the method according to any one of claims 1 to 7, characterized in that: include: A single crystal silicon substrate; a narrow-bandgap quantum dot sensitizing layer coated on the surface of the single crystal silicon substrate, wherein the quantum dot sensitizing layer is modified with short-chain ligands to achieve gradient energy band matching with the silicon substrate; two back-to-back metal electrodes form Schottky contacts with the quantum dot sensitizing layer, respectively, to form a double Schottky junction structure; the double Schottky junction achieves self-powered near-infrared light detection under zero bias through a built-in electric field.

9. Use of the quantum dot-sensitized silicon-based double Schottky junction near-infrared detector according to claim 8 in a silicon-based device integrated system.

Images