Silicon oxide microsphere array enhanced germanium detector and preparation method thereof

Abstract

The invention belongs to the technical field of photon detection, and relates to a silicon oxide microsphere array enhanced germanium detector and a preparation method thereof. The method specifically comprises the following steps: carrying out chemical cleaning on a Si single crystal wafer; monodispersing silicon oxide powder in water to prepare a microsphere solution; coating the silicon single crystal wafer with the microsphere solution to prepare a silicon oxide microsphere array; transferring the silicon oxide microsphere array to a polydimethylsiloxane adhesive tape, and then transferring the silicon oxide microsphere array to the surface of the germanium detector body to obtain a silicon oxide microsphere array enhanced germanium detector structure; the preparation cost is low, and the obtained silicon oxide microsphere array enhanced germanium detector is high in performance.

Description

Technical Field

[0001] The invention belongs to the technical field of photon detection, and relates to a silicon oxide microsphere array-enhanced germanium detector and a preparation method thereof. Background Art

[0002] As a key component in the optical fiber communication system, efficient infrared detectors with detection wavelengths in the range of 900-1600 nanometers (nm) play a vital role. Such detectors can not only achieve high-speed data transmission, but also show wide application potential in many fields such as remote sensing, environmental monitoring, and medical diagnosis. Therefore, the optimization and improvement of their performance has always been a hot topic in scientific research and industry.

[0003] Silicon (Si) and germanium (Ge) materials have long been regarded as ideal materials for photodetection in the telecommunications field due to their suitable bandgap width and good compatibility with existing commercial complementary metal oxide semiconductor (CMOS) technology. In the wavelength range of 900-1600nm, germanium can exhibit good light absorption characteristics, making them the first choice for photodetectors in this band. However, when the wavelength is further extended to 1600-2000nm, due to the limitation of the bandgap width, the imaginary part of the refractive index of the germanium material is significantly reduced, resulting in a sharp drop in its light absorption efficiency. This phenomenon poses a severe challenge to the application of germanium-based photodetectors, especially in situations where high-sensitivity detection is required.

[0004] In order to improve the quantum efficiency of germanium in the spectral range near the absorption edge, the existing technology usually prepares a nanoarray structure on the surface of the germanium detector. This structure is called a light-trapping structure. The light-trapping structure can significantly improve the absorption efficiency of the germanium material by increasing the interaction path length between light and the material, thereby improving the detection efficiency of the detector. For example, by preparing a silicon-based nanocolumn array or nanocone array on the surface of the germanium detector, the light capture and conversion efficiency can be significantly enhanced, so that more light energy can be converted into electrical energy.

[0005] However, the preparation process of these periodic nanostructures is not easy. They usually need to be realized through micro-nano processing technologies such as photolithography or electron beam exposure, which are not only costly but also complex. In addition, the etching process is an indispensable step in the pattern preparation process. However, the etching process often introduces interface defects, which increase the recombination efficiency of carriers, thereby increasing the dark current of the device. The increase in dark current will seriously affect the key performance of the device, such as the signal-to-noise ratio and detection rate, which limits the practical application of the detector. Therefore, how to reduce the preparation cost and reduce the generation of interface defects while maintaining efficient light absorption has become a major problem in the current research of silicon-based photodetectors. Summary of the invention

[0006] In order to solve the limitation of preparing nanostructure arrays on the surface of germanium detectors, the object of the present invention is to provide a low-cost, high-efficiency silicon oxide microsphere array-enhanced germanium detector and a preparation method thereof.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for preparing a silicon oxide microsphere array enhanced germanium detector, which specifically comprises the following steps: The Si single crystal wafer is chemically cleaned; the silicon oxide powder is dispersed in water to prepare a microsphere solution; the microsphere solution is coated on the Si single crystal wafer to prepare a silicon oxide microsphere array; the silicon oxide microsphere array is transferred to a polydimethylsiloxane tape, and then transferred to the surface of the germanium detector body, finally preparing a germanium detector structure enhanced by a silicon oxide microsphere array.

[0008] Preferably, the crystal orientation of the Si single crystal wafer is 001.

[0009] Preferably, the concentration of the microsphere solution is 5 wt%~30 wt%.

[0010] Preferably, the microspheres have a diameter of 300-3000 nm.

[0011] Preferably, the water is deionized water.

[0012] In a second aspect, the present invention provides a germanium detector enhanced by a silicon oxide microsphere array, comprising a germanium detector body and a passivation layer and a second metal electrode spaced apart on the top thereof; a silicon oxide microsphere array is disposed on the top of the passivation layer.

[0013] Preferably, the passivation layer material is polydimethylsiloxane.

[0014] Preferably, the germanium detector body includes, from bottom to top, a first metal electrode, an N-Ge layer and a P-Ge layer.

[0015] Preferably, the orthographic projection of the P-Ge layer on the first metal electrode overlaps with the orthographic projection of the N-Ge layer on the first metal electrode.

[0016] Preferably, the germanium detector body is a metal-semiconductor-metal type germanium detector, a PN junction type germanium detector, a PIN junction type or a separation-absorption-charge-multiplication type germanium detector.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The invention uses a nanostructure array with a width of centimeters to be prepared by self-assembly technology of silicon oxide microspheres. The preparation process of the silicon oxide microsphere array is completely independent of the germanium detector, thereby avoiding the influence of secondary micro-nano processing on the surface of the germanium detector on the photoelectric performance of the germanium detector, such as the increase of dark current. The silicon oxide microsphere array can be transferred to the germanium detector body by dry transfer and maintain uniformity. The silicon oxide microspheres of the invention have uniform sizes and low costs. At the same time, micro-nano processing technologies such as photolithography, electron beam exposure and etching can be avoided, thereby avoiding surface defects. In addition, the preparation cost is low, and the germanium detector enhanced by the silicon oxide microsphere array has high performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 It is a schematic structural diagram of a germanium detector enhanced by a silicon oxide microsphere array of the present invention; Figure 2 is a cross-sectional view of a silicon oxide microsphere array on a Si single crystal wafer in the present invention; Figure 3 It is a top view of the silicon oxide microsphere array on the Si single crystal wafer in the present invention.

[0020] In the figure, 1, first metal electrode; 2, N-Ge layer; 3, P-Ge layer; 4, passivation layer; 5, silicon oxide microsphere array; 6, second metal electrode. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0024] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0025] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0026] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The first object of the present invention is to provide a method for preparing a silicon oxide microsphere array enhanced germanium detector, which specifically comprises the following steps: The Si single crystal wafer is chemically cleaned; the silicon oxide powder is dispersed in water, preferably deionized water, to prepare a microsphere solution with a concentration of 5 wt% to 30 wt%; the microsphere solution is coated on the Si single crystal wafer to prepare a silicon oxide microsphere array 5; the silicon oxide microsphere array 5 is transferred to a polydimethylsiloxane (PDMS) tape, and then transferred to the surface of the germanium detector body to obtain a silicon oxide microsphere array-enhanced germanium detector structure.

[0028] Chemical cleaning can remove impurities, oil stains and oxides on the surface of Si single crystal wafers, ensuring the cleanliness of the surface of Si single crystal wafers. By preferably using deionized water as a solvent and controlling the concentration of silicon oxide powder between 5 wt% and 30 wt%, good monodispersity of silicon oxide powder in water can be achieved. At the same time, this concentration range can ensure that the microsphere solution has suitable viscosity and fluidity when coated, thereby obtaining a uniform and dense microsphere array. The introduction of silicon oxide microsphere array 5 can increase the light absorption rate of the detector, thereby improving its detection ability of the target substance. At the same time, the uniformity of silicon oxide microsphere array 5 also helps to improve the stability and sensitivity of the detector. Secondly, the resonant wavelength of silicon oxide microsphere array 5 can be regulated by controlling the size of silicon oxide microspheres, so it is suitable for detection enhancement in a large wavelength range from visible to infrared bands. The silicon oxide microsphere array-enhanced germanium detector prepared by the invention can solve the shortcomings of the existing light trapping structure, effectively improve the efficiency of the germanium detector, and has great potential for application in optical communications, laser radar, night vision and other applications. The polydimethylsiloxane tape has good flexibility and adhesion, and can easily realize the transfer of the silicon oxide microsphere array 5, while avoiding damage to the microsphere array, and ensuring its uniformity and stability on the surface of the germanium detector body. The polydimethylsiloxane tape has good compatibility and sealing properties with silicon, germanium and other semiconductor detector bodies, and can ensure close contact between the silicon oxide microsphere array 5 and the detector body, which helps to improve the sensitivity and response speed of the detector, while preventing interference from the external environment.

[0029] Among them, the crystal orientation of the Si single crystal wafer is 001, which can ensure its stability and consistency in physical and chemical properties.

[0030] The diameter of the microspheres is 300-3000 nm. Within this diameter range, the silica microspheres can provide sufficient surface area and porosity to enhance the capture and detection capabilities of the detector. At the same time, it also helps to improve the sensitivity and response speed of the detector.

[0031] The size of the silicon oxide periodic array prepared by the spin coating method of the present invention can reach the centimeter level, so it is suitable for surface enhancement of unit devices, linear array detectors and large-size area array detectors. In the preparation process, the present invention strictly follows the standard process of chemical cleaning, that is, the industry-recognized RCA (Radio Corporation of America) cleaning method is adopted, which has an efficient and thorough cleaning effect, and can completely remove various pollutants on the substrate surface, including organic matter, metal ions and particulate impurities, etc., and provide a clean and flawless substrate surface for the subsequent spin coating process, thereby ensuring the high-quality preparation of the silicon oxide periodic array. As for the preparation of the silicon oxide microsphere array 5, the present invention is not limited to the spin coating method, but is also compatible with other self-assembly methods. The spin coating method has the advantages of simple operation, low cost and easy control of film thickness and uniformity. However, in order to meet the diverse needs in different application scenarios, the present invention also supports the use of other self-assembly technologies, such as electrostatic self-assembly, capillary self-assembly, etc., to further broaden the preparation method of the silicon oxide periodic array and optimize its performance.

[0032] The second object of the present invention is to provide a germanium detector enhanced by a silicon oxide microsphere array, comprising a germanium detector body and a passivation layer 4 and a second metal electrode 6 spaced apart on the top thereof; a silicon oxide microsphere array 5 is arranged on the top of the passivation layer 4. The germanium detector body has excellent photoelectric conversion performance and can efficiently convert incident photons into electrical signals. Its high sensitivity and rapid response characteristics make the detector have broad application prospects in the fields of photoelectric detection, spectral analysis, etc. The passivation layer 4 is located on the top of the germanium detector body and plays a key protective role. It can effectively isolate the influence of impurities, water vapor, etc. in the external environment on the germanium detector body, and improve the stability and service life of the detector. At the same time, the passivation layer 4 also has good insulation properties, which prevents the leakage of electrons inside the detector and further improves the performance of the detector. Figure 2 and Figure 3 As shown, the microspheres of the silicon oxide microsphere array 5 have uniform size and shape, and can accurately control the incident angle and path of photons, thereby improving the light capture efficiency of the detector. In addition, the silicon oxide microsphere array 5 also plays a role in enhancing transmittance and scattering, so that more photons can be absorbed by the germanium detector body, further improving the sensitivity of the detector. At the same time, the introduction of the silicon oxide microsphere array 5 also increases the surface area of ​​the detector, which is beneficial to heat dissipation and noise reduction. The second metal electrode 6 serves as the output end of the detector, responsible for collecting and deriving the electrical signal generated by the germanium detector body. Its good electrical conductivity and close contact with the germanium detector body ensure the efficient transmission of electrical signals. In addition, the introduction of the second metal electrode 6 also improves the mechanical strength and stability of the detector.

[0033] The material of the passivation layer 4 is aluminum oxide, silicon oxide or silicon nitride. These materials have excellent chemical stability and weather resistance, and can resist the corrosion of acids, alkalis, oxidants and other substances in the external environment, thereby protecting the germanium detector body from damage and improving the overall stability and service life of the detector. Secondly, these materials have high transparency and the transmittance can exceed 90%. They will not block or absorb incident photons, but allow photons to pass smoothly and reach the germanium detector body, which helps to enhance the light capture efficiency of the detector and improve the detection sensitivity. Aluminum oxide, silicon oxide and silicon nitride have excellent electrical insulation properties, which can effectively isolate the electron leakage inside the detector and external electromagnetic interference, thereby reducing the noise level of the detector and improving the signal-to-noise ratio.

[0034] The germanium detector body includes, from bottom to top, a first metal electrode 1, an N-Ge layer 2, and a P-Ge layer 3. As the core part of the detector, the N-Ge layer 2 and the P-Ge layer 3 form a PN junction, which can effectively distinguish and collect charge carriers of different polarities, thereby improving the sensitivity and response speed of the detector. At the same time, the first metal electrode 1, as the input / output terminal of the current, forms a good ohmic contact with the N-Ge layer 2, ensuring the smooth transmission of the current and further improving the overall performance of the detector. Ohmic contact is an ideal form of electrical contact, which can achieve low-resistance transmission of current on the contact interface, avoiding unnecessary energy loss and signal distortion. This design further optimizes the current transmission efficiency of the detector and reduces noise interference, thereby further improving the overall performance of the detector, including its stability, accuracy and reliability.

[0035] The orthographic projection of the P-Ge layer 3 on the first metal electrode 1 overlaps with the orthographic projection of the N-Ge layer 2 on the first metal electrode 1. Specifically, the N-Ge layer 2 covers the upper surface and side surfaces of the P-Ge layer 3. Due to the difference in the characteristics of P-type and N-type semiconductor materials, when stimulated by external radiation or signals, obvious charge separation and collection effects will occur. The presence of the coating increases the effective area of ​​the PN junction, thereby improving the detector's ability to capture external signals and conversion efficiency. In addition, this structure also helps to optimize the electric field distribution of the detector, so that charge carriers can be collected and transmitted more efficiently, further improving the sensitivity and response speed of the detector.

[0036] The germanium detector body is a metal-semiconductor-metal germanium detector, a PN junction germanium detector, a PIN junction or a separation-absorption-charge-multiplication germanium detector. The metal-semiconductor-metal (MSM) germanium detector is a detector based on a Schottky barrier structure formed by the contact between metal and semiconductor. It forms a barrier by making a metal electrode on a germanium semiconductor material and using the energy level difference between metal and germanium to detect incident photons. It has the advantages of simple structure, relatively easy preparation process, fast response speed, etc., and is suitable for high-speed and high-sensitivity photoelectric detection applications. The PN junction germanium detector is a device that uses the PN junction characteristics of silicon and germanium materials to detect photons. In the PN junction germanium detector, P-type germanium and N-type germanium are combined together through a specific process to form a PN junction. When the incident photon irradiates the PN junction, the photon energy is absorbed by the germanium material, exciting electron-hole pairs. These electrons and holes move to the two poles respectively under the action of the built-in electric field of the PN junction to form a photocurrent, thereby realizing the detection of light signals. PN junction germanium detectors have the advantages of high detection sensitivity and good stability, and are widely used in optical communications, spectral analysis and other fields. PIN junction germanium detectors are formed by inserting an intrinsic (I) germanium layer between the P region and the N region on the basis of PN junction germanium detectors. This intrinsic germanium layer has a wide depletion region, which can more effectively collect electron-hole pairs generated by incident photons, thereby improving the quantum efficiency and sensitivity of the detector. PIN junction germanium detectors perform well in high-speed, high-sensitivity, and low-noise photodetection applications. Separation-absorption-charge-multiplication (SACM) germanium detectors are high-performance photodetectors that combine separation, absorption and charge multiplication functions. It achieves amplification and detection of weak light signals by separating incident photons into electrons and holes in a specific absorption layer, and then multiplying electrons or holes using a multiplication layer. SACM germanium detectors have extremely high sensitivity and gain, and are suitable for photodetection applications under extremely low light intensities, such as night vision devices and astronomical observations.

[0037] The present invention utilizes the self-assembly characteristics of silicon oxide microspheres to prepare a periodic array on a silicon substrate, and utilizes a dry transfer technology to transfer the silicon oxide microsphere array 5 to the surface of a germanium detector, and finally prepares a germanium detector enhanced by a silicon oxide microsphere array. The germanium detector enhanced by the silicon oxide microsphere array of the present invention can prepare a periodic array because of the self-assembly characteristics of the silicon oxide microspheres, and due to the van der Waals force between the silicon oxide surface and the germanium detector surface, silicon oxide can be transferred to the surface of the germanium detector, avoiding micro-nano processing technologies such as photolithography, electron beam exposure and etching, thereby avoiding surface defects, and thus being able to prepare a low-cost, high-performance silicon oxide microsphere array enhanced germanium detector.

[0038] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a silicon oxide microsphere array enhanced germanium detector, characterized in that: The specific steps include: The Si single crystal wafer is chemically cleaned; silicon oxide powder is dispersed in water to prepare a microsphere solution; the microsphere solution is coated on the Si single crystal wafer to prepare a silicon oxide microsphere array (5); the silicon oxide microsphere array (5) is transferred to a polydimethylsiloxane tape, and then transferred to the surface of a germanium detector body to obtain a germanium detector structure enhanced by a silicon oxide microsphere array.

2. The method for preparing a silicon oxide microsphere array enhanced germanium detector according to claim 1, characterized in that: The crystal orientation of the Si single crystal wafer is 001.

3. The method for preparing a silicon oxide microsphere array enhanced germanium detector according to claim 1, characterized in that: The concentration of the microsphere solution is 5 wt% to 30 wt%.

4. The method for preparing a silicon oxide microsphere array enhanced germanium detector according to claim 1, characterized in that: The diameter of the microspheres is 300-3000 nm.

5. The method for preparing a silicon oxide microsphere array enhanced germanium detector according to claim 1, characterized in that: The water is deionized water.

6. A silicon oxide microsphere array enhanced germanium detector, characterized in that: It comprises a germanium detector body and a passivation layer (4) and a second metal electrode (6) arranged at intervals on the top of the germanium detector body; a silicon oxide microsphere array (5) is arranged on the top of the passivation layer (4).

7. The silicon oxide microsphere array enhanced germanium detector according to claim 6, characterized in that: The material of the passivation layer (4) is aluminum oxide, silicon oxide or silicon nitride.

8. The silicon oxide microsphere array enhanced germanium detector according to claim 6, characterized in that: The germanium detector body comprises, from bottom to top, a first metal electrode (1), an N-Ge layer (2) and a P-Ge layer (3).

9. The silicon oxide microsphere array enhanced germanium detector according to claim 8, characterized in that: The orthographic projection of the P-Ge layer (3) on the first metal electrode (1) overlaps with the orthographic projection of the N-Ge layer (2) on the first metal electrode (1).

10. The silicon oxide microsphere array enhanced germanium detector according to claim 6, characterized in that: The germanium detector body is a metal-semiconductor-metal type germanium detector, a PN junction type germanium detector, a PIN junction type or a separation-absorption-charge-multiplication type germanium detector.

Images