Silicon-based wide-spectrum detector array and preparation method thereof

Abstract

The present invention discloses a silicon-based wide spectrum detector array and a preparation method thereof, which is composed of a plurality of detector unit arrays, each detector unit comprising an SOI substrate, a silicon dioxide window layer, a long-wave absorption layer, an n-electrode and a p-electrode, the SOI substrate comprising a bottom Si material layer, a silicon dioxide buried layer and a top silicon layer, the top silicon layer comprising an n-type heavily doped region, an n-type medium doped region and an intrinsic region. The present invention adopts partial doping and light doping on the surface of the active region of the light-receiving surface, and retains part of the intrinsic region, so that there is no dead zone effect of short-wave detection in the intrinsic non-injection region, which can effectively improve the response of the spectrum detector to the optical signal with a shorter wavelength, thereby realizing the wide spectrum detection of 300nm-2000nm.

Description

Technical Field

[0001] The invention relates to a detector array and a preparation method thereof, in particular to a silicon-based wide-spectrum detector array and a preparation method thereof, belonging to the field of optoelectronic technology. Background Art

[0002] Wide-spectrum multicolor imaging and detection have broad application prospects in high-quality portrait photography, agriculture, military, environmental monitoring, geological exploration, marine remote sensing, atmospheric remote sensing, biomedicine, etc., and have become a research hotspot in the field of optoelectronics in recent years. Generally speaking, a semiconductor material can only respond to and detect light within a specific wavelength range. In order to achieve wide-spectrum detection, different semiconductor materials must be integrated to expand the light response range. Current photodetectors generally use direct bandgap III-V semiconductor materials, such as InGaAs, InSb, InAs and other materials. High-efficiency wide-spectrum detection can be achieved through heteroepitaxial integration of III-V materials with different bandgap widths. By integrating an array of wide-spectrum detectors with a silicon microelectronic detector readout circuit, wide-spectrum imaging can be achieved, which will greatly increase the application range of wide-spectrum detectors. Unfortunately, although direct-bandgap III-V materials have good detection efficiency, they are relatively expensive, have poor thermal and mechanical properties, and most importantly, cannot be compatible with silicon microelectronic chips, which greatly limits their application.

[0003] Since the band gap of silicon is 1.12eV, it cannot effectively absorb light signals with wavelengths greater than 1100nm. In addition, although silicon can absorb short-wavelength light signals (<400nm), its penetration depth in silicon is very limited. Therefore, silicon detectors can usually only effectively detect light signals of 400nm-1100nm. Germanium, which is also a group IV element, has a higher response in the near-infrared band, and germanium detectors can effectively detect light signals of 800nm-1700nm. Using germanium-tin alloy detectors, light signals of 800nm-2000nm can be effectively detected. Moreover, both germanium and germanium-tin alloys can be epitaxially grown on silicon and are fully compatible with existing silicon CMOS processes, which can effectively reduce costs. Therefore, through the reasonable integration of silicon, germanium and germanium-tin alloys, and by making full use of the light detection capabilities of materials in different bands, the response wavelength of silicon-based detectors can be broadened to 400nm-2000nm, realizing wide spectrum detection.

[0004] Therefore, if the dead zone effect caused by surface doping can be reduced, the corresponding wavelength range of silicon-based detectors can be further broadened. However, in the traditional vertical PIN structure, the outermost surface of the active area of ​​the detector has a heavily doped or medium-doped layer. For optical signals with shorter wavelengths or even in the ultraviolet band (<400nm), the photogenerated carriers generated by the light signal absorbed by the material are gathered in the surface doped area and are difficult to extract, resulting in the lack of spectral response of the detector at short wavelengths. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a silicon-based wide-spectrum detector array and a preparation method thereof, so as to improve the response of the spectrum detector to light signals with shorter wavelengths and realize wide-spectrum detection of 300nm-2000nm.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A silicon-based wide spectrum detector array, characterized in that: it is composed of a plurality of detector unit arrays, each detector unit comprises an SOI substrate, a silicon dioxide window layer, a long-wave absorption layer, an n-electrode and a p-electrode, the SOI substrate comprises a bottom Si material layer, a silicon dioxide buried layer and a top silicon layer, the silicon dioxide buried layer is made on the upper side of the bottom Si material layer, the top silicon layer is made on the upper side of the silicon dioxide buried layer, wherein the bottom Si material layer partially covers the lower side of the silicon dioxide buried layer, the top silicon layer comprises an n-type heavily doped region, an n-type The n-type medium doped region and the intrinsic region, the n-type heavily doped region completely replaces the top silicon within a depth range, the n-type medium doped region and the intrinsic region are arranged in the hollow region between the n-type heavily doped regions and the intrinsic region is located on the upper side of the n-type medium doped region, the shape of the silicon dioxide window layer matches the n-type heavily doped region and is correspondingly made on the upper side of the n-type heavily doped region, the lower outer edge of the long-wave absorption layer grows in the silicon dioxide window layer and completely covers the n-type medium doped region and the upper side of the intrinsic region, the n-electrode is made on the n-type medium doped region, and the p-electrode is made on the top of the long-wave absorption layer.

[0008] Furthermore, the n-type heavily doped region is distributed in a rectangular shape on the outer edge of a single detector unit, the n-type medium doped region is distributed in a geometric shape in the hollow region inside the n-type heavily doped region, the lower side of the n-type medium doped region is located on the upper side of the silicon dioxide buried layer and the n-type medium doped region partially replaces the top silicon within a depth range, and the hollow region inside the n-type heavily doped region is entirely intrinsic region except for the n-type medium doped region.

[0009] Furthermore, a p-type doping region is provided on the top of the long-wave absorption layer, and a p-electrode is manufactured on the p-type doping region.

[0010] Furthermore, it also includes an insulating dielectric layer, which is arranged on the outside of the silicon dioxide window layer and the long-wave absorption layer.

[0011] Furthermore, the bottom Si material layer and the long-wave absorption layer are staggered.

[0012] Furthermore, the material of the long-wave absorption layer is pure germanium, germanium-tin alloy or germanium-silicon alloy.

[0013] A method for preparing a silicon-based wide-spectrum detector array, characterized by comprising the following steps:

[0014] S1, respectively making an n-type heavily doped region and an n-type medium doped region on the top silicon layer, and the undoped region is the intrinsic region;

[0015] S2, depositing silicon dioxide on the surface of the top silicon to form a silicon dioxide window layer, and opening windows on the silicon dioxide window layer corresponding to the n-type middle doped region and the region above the intrinsic region;

[0016] S3, selectively epitaxially growing a long-wave absorption layer on the top silicon exposed in the window of the silicon dioxide window layer;

[0017] S4, making a p-type doped region on the top of the long-wave absorption layer;

[0018] S5, depositing an insulating dielectric layer on the long-wave absorption layer and the silicon dioxide window layer;

[0019] S6. Making an n-electrode common to all detector units on the top silicon layer corresponding to the n-type heavily doped region, wherein the n-electrode is electrically connected to the n-type heavily doped region;

[0020] S7, making an independent p-electrode on the p-type doping region of each detector unit, and the p-electrode is electrically connected to the p-type doping region;

[0021] S8, annealing to form ohmic contact;

[0022] S9, thinning the bottom Si material layer and removing the corresponding Si material layer below the long-wave absorption layer to complete the preparation.

[0023] Furthermore, in step S1, the thickness of the top silicon layer is greater than 200 nm, the thickness of the silicon dioxide buried layer is greater than 300 nm, and the crystal orientation of the top silicon layer 110 is <001> direction, the conductivity type of the top silicon is p-type, the resistivity is 10 ohms / cm, the injection depth of the n-type heavily doped region is 0 to 340nm, and the doping concentration is greater than 1×10 19 cm -3 The ion implantation depth of the n-type doping region is 200-340 nm, and the doping concentration is greater than 1×10 18 cm -3 The high temperature annealing activation condition is >800 ℃ / 10min.

[0024] Furthermore, in step S2, silicon dioxide is deposited on the top silicon surface by an ion enhanced chemical vapor deposition system or a thermal oxidation method, and windows are opened on the silicon dioxide on the upper side of the n-type doped region and the intrinsic region by using a photoresist as a mask and a combination of dry and wet etching methods.

[0025] Furthermore, in step S3, an ultra-high vacuum chemical vapor deposition system is used to epitaxially grow a long-wave absorption layer in the window of the silicon dioxide window layer.

[0026] Furthermore, in the step S8, the annealing temperature is 150-750°C.

[0027] Furthermore, in step S9, a mechanical grinding process is used to thin the bottom Si material layer, and then a photoresist is used as a mask and dry etching is performed to remove the corresponding Si material layer below the long-wave absorption layer to complete the preparation.

[0028] Compared with the prior art, the present invention has the following advantages and effects: the silicon-based wide-spectrum detector array of the present invention adopts partial doping and shallow doping on the surface of the active area of ​​the light-receiving surface, and retains part of the intrinsic area, so that there is no dead zone effect of short-wave detection in the intrinsic non-injection area, and can effectively improve the response of the spectrum detector to the optical signal with shorter wavelength, thereby realizing wide-spectrum detection of 300nm-2000nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a silicon-based wide-spectrum detector array of the present invention.

[0030] Figure 2 1 and 2 are top views of several forms of the top silicon layer of the present invention.

[0031] Figure 3 The present invention is a flow chart of a method for preparing a silicon-based wide-spectrum detector array. DETAILED DESCRIPTION

[0032] In order to elaborate on the technical scheme adopted by the present invention to achieve the predetermined technical purpose, the technical scheme 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 only partial embodiments of the present invention, rather than all embodiments, and the technical means or technical features in the embodiments of the present invention can be replaced without paying creative work. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0033] like Figure 1As shown, a silicon-based wide spectrum detector array of the present invention is composed of a plurality of detector unit arrays, each detector unit comprises an SOI substrate 1, a silicon dioxide window layer 2, a long-wave absorption layer 3, an n-electrode 4 and a p-electrode 5, the SOI substrate 1 comprises a bottom Si material layer 11, a silicon dioxide buried layer 12 and a top silicon layer 13, the silicon dioxide buried layer 12 is made on the upper side of the bottom Si material layer 11, and the top silicon layer 13 is made on the upper side of the silicon dioxide buried layer 12. The bottom Si material layer 11 partially covers the lower side of the silicon dioxide buried layer 12, the top silicon layer 13 comprises an n-type heavily doped region 14, an n-type medium doped region 15 and an intrinsic region 16, the n-type heavily doped region 14 completely replaces the top silicon layer 13 within a depth range, and is used to isolate adjacent detectors, prevent photogenerated carriers from crossing between adjacent detectors and causing crosstalk, and improve the clarity of imaging. The n-type medium doping region 15 and the intrinsic region 16 are arranged in the hollow region between the n-type heavily doped regions 14, and the intrinsic region 16 is located on the upper side of the n-type medium doping region 15. The shape of the silicon dioxide window layer 2 matches the n-type heavily doped region 14 and is correspondingly made on the upper side of the n-type heavily doped region 14. In order to avoid the silicon dioxide window layer 2 from affecting the n-type medium doping region, the width of the silicon dioxide window layer 2 is smaller than the n-type heavily doped region 14, so that it partially covers the n-type heavily doped region 14. The preparation method of the silicon dioxide window layer 2 can be achieved by thermal oxidation of the top silicon 13, sputtering growth or chemical vapor deposition. The epitaxial window of the silicon dioxide window layer 2 can be formed by HF etching or dry etching. By using HF etching, the surface roughness and defects introduced by dry etching can be avoided, thereby improving the quality of the subsequent extended wave absorption layer 3. The shape of the top silicon 13 exposed in the etched silicon dioxide window layer 2 determines the position and area of ​​the subsequent extended wave absorption layer 3. The shape of the silicon dioxide window layer 2 is preferably square or rectangular, which can effectively improve the detection area duty ratio of the detector array.

[0034] The lower outer edge of the long-wave absorption layer 3 is grown in the silicon dioxide window layer 2 and completely covers the n-type medium-doped region 15 and the upper side of the intrinsic region 16. The n-electrode 4 is made on the n-type medium-doped region 15 to form a good ohmic contact with the n-type heavily doped region 15. The p-electrode 5 is made on the top of the long-wave absorption layer 3 to form a good ohmic contact with the p-type doped region 6.

[0035] The optical signal is incident from the direction of the silicon dioxide buried layer 12, and first passes through the top silicon 13. The optical signal that cannot be absorbed or cannot be completely absorbed by the top silicon 13 will enter the long-wave absorption layer 3 for absorption. At this time, the incompletely absorbed optical signal will be reflected by the p-electrode 5 on the top of the germanium detector, and enter the detector again for secondary absorption, thereby improving the responsivity. Usually, silicon detectors can only effectively detect optical signals of 400nm-1100nm, germanium detectors can effectively detect optical signals of 800nm-1700nm, and germanium-tin detectors can increase the effective detection wavelength to 2000nm and above.

[0036] like Figure 2 As shown, the n-type heavily doped region 14 is distributed in a rectangular shape on the outer edge of a single detector unit. On the entire detector array, the n-type heavily doped region 14 is in a rectangular grid shape, divided into small square grids, and each small grid is a detector unit. The n-type medium doped region 15 is distributed in a geometric shape in the hollow area inside the n-type heavily doped region 14. Figure 2 Several geometric shapes of the n-type medium doping region 15 are listed. The lower side of the n-type medium doping region 15 is located on the upper side of the silicon dioxide buried layer 12 and the n-type medium doping region 15 partially replaces the top silicon 13 within the depth range, which is used to reduce the depth of the n-type medium doping region and reduce its influence on the extraction of photogenerated carriers. The hollow area inside the n-type heavily doped region 14 is all the intrinsic region 16 except the n-type medium doping region 15.

[0037] A p-type doping region 6 is provided on the top of the long-wave absorption layer 3, and a p-electrode 5 is fabricated on the p-type doping region 6. The p-type doping region is activated by annealing after being implanted with boron and gallium ions by ion implantation. The doping concentration of the p-type doping region is greater than 5×10 18 / cm 3 .

[0038] The silicon-based wide spectrum detector array of the present invention further comprises an insulating dielectric layer 7, which is arranged outside the silicon dioxide window layer 2, the long-wave absorption layer 3 and the p-type doping region 6 to achieve electrical isolation from the external environment. A through hole is reserved on the upper side of the p-type doping region 6 for the p-electrode 5 to pass through.

[0039] The bottom Si material layer 11 is staggered with the long-wave absorption layer 3. Since the bottom Si material layer 11 can also absorb a portion of the optical signal, the bottom Si material layer 11 below the long-wave absorption layer 3 of the detector array is removed to eliminate the effect of the silicon substrate on the optical response of the detector. The material of the long-wave absorption layer 3 is pure germanium, germanium-tin alloy or germanium-silicon alloy.

[0040] The n-type medium doping region 15 and the n-type heavily doped region 14 can be formed by ion implantation or impurity diffusion. Preferably, in this embodiment, the n-type heavily doped region 14 and the n-type medium doping region 15 are implanted with phosphorus or arsenic ions by ion implantation and then activated by annealing, wherein the doping concentration of the n-type medium doping region is greater than 1×10 17 / cm 3 The n-type heavily doped region has a doping concentration greater than 5×10 18 / cm 3 .

[0041] like Figure 3 As shown, a method for preparing a silicon-based wide-spectrum detector array comprises the following steps:

[0042] S1. Use photoresist as a mask and ion implantation to form an n-type heavily doped region 14 and an n-type medium doped region 15 on the top silicon 13. The undoped region is the intrinsic region 16. The thickness of the top silicon 13 is greater than 200nm, and the thickness of the silicon dioxide buried layer 12 is greater than 300nm. In this embodiment, the thickness of the silicon dioxide buried layer 12 is 2 μm, the thickness of the top silicon 13 is 340nm, and the crystal orientation of the top silicon 13 is <001> direction, the conductivity type is p-type, and the resistivity is 10 ohm / cm. The implantation depth of the n-type heavily doped region 14 is 0 to 340 nm, and the doping concentration is greater than 1×10 19 cm -3 The ion implantation depth of the n-type doping region 15 is 200-340 nm, and the doping concentration is greater than 1×10 18 cm -3 The high temperature annealing activation condition is >800 ℃ / 10min.

[0043] S2. Silicon dioxide is deposited on the surface of the top silicon 13 by a plasma enhanced chemical vapor deposition system (PECVD) or a thermal oxidation method, and a silicon dioxide window layer 2 is made on the silicon dioxide on part of the n-type heavily doped region 14, the n-type medium doped region 15 and the intrinsic region 16 by using a photoresist as a mask and a dry and wet etching method for preparing the long-wave absorption layer 3. In this embodiment, the thickness of silicon dioxide is 200 nm, and the shape of the detector unit is square, so the shape of the silicon dioxide etching window is square, which occupies more than 75% of the area of ​​a single detector.

[0044] S3, after cleaning, put it into an ultra-high vacuum chemical vapor deposition system (UHV-CVD), and epitaxially grow a long-wave absorption layer 3 on the top silicon 13 in the epitaxial window of the silicon dioxide window layer 2. The material of the long-wave absorption layer 3 is pure germanium, germanium-tin alloy or germanium-silicon alloy, and the thickness of the long-wave absorption layer 3 is at least greater than 200nm. In this embodiment, the long-wave absorption layer 3 uses pure germanium material. In order to improve the responsivity of the detector at 1100-1700nm, the thickness of the long-wave absorption layer is 800nm, and at a wavelength of 1550nm, a responsivity greater than 0.6A / W can be obtained.

[0045] S4, using photoresist as a mask and ion implantation to form a p-type doping region 6 on the top of the long-wave absorption layer 3. In this embodiment, the implanted ions in the p-type doping region 6 are boron, the implantation depth is 0 to 100 nm, and the doping concentration is greater than 1×10 19 cm -3 The conditions for rapid annealing activation are >400 ℃ / 1min.

[0046] S5, depositing an insulating dielectric layer 7 on the long-wave absorption layer 3 and the silicon dioxide window layer 2 to achieve electrical isolation from the external environment. In this embodiment, PECVD is used to deposit 400 nm of silicon dioxide.

[0047] S6 , manufacturing an n-electrode 4 shared by all detector units on the top silicon layer 13 corresponding to the n-type heavily doped region 14 , and forming an electrical connection with the n-type heavily doped region 14 .

[0048] S7 . A p-electrode 5 is independently provided for each detector unit on the p-type doping region 6 , and is electrically connected to the p-type doping region 6 .

[0049] S8, annealing to form ohmic contact. The annealing temperature in this embodiment is 150-750° C., so as to achieve ohmic contact between the n-electrode 4 and the n-type heavily doped region 14 and between the p-electrode 5 and the p-type doped region 6.

[0050] S9, thinning the bottom Si material layer 11 by mechanical grinding, and then removing the corresponding bottom Si material layer 11 below the long-wave absorption layer 3 by dry etching using photoresist as a mask, to complete the preparation. In this embodiment, the bottom Si material layer 11 is thinned to 150 μm, and then the corresponding bottom Si material layer 11 is completely removed by backside photolithography and dry etching.

[0051] The present invention provides a silicon-based wide-spectrum detector array and a preparation method thereof. Partial doping and shallow doping are used on the surface of the active area of ​​the light-receiving surface, and part of the intrinsic area is retained. Therefore, in the intrinsic non-injection area, there is no dead zone effect of short-wave detection, which can effectively improve the response of the detector to light signals with shorter wavelengths, thereby realizing wide-spectrum detection of 300nm-2000nm. In addition, the present invention uses silicon as a substrate and can utilize the powerful electrical signal processing ability of silicon in the field of microelectronics, providing a good integration foundation and optimization space for the arraying of silicon-based wide-spectrum detectors in the future, and has broad application prospects in the fields of silicon-based wide-spectrum light processing and optical imaging.

[0052] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A silicon-based wide spectrum detector array, characterized in that: The invention is composed of a plurality of detector unit arrays, each of which comprises an SOI substrate, a silicon dioxide window layer, a long-wave absorption layer, an n-electrode and a p-electrode. The SOI substrate comprises a bottom Si material layer, a silicon dioxide buried layer and a top silicon layer. The silicon dioxide buried layer is made on the upper side of the bottom Si material layer, and the top silicon layer is made on the upper side of the silicon dioxide buried layer. The bottom Si material layer partially covers the lower side of the silicon dioxide buried layer. The top silicon layer comprises an n-type heavily doped region, an n-type medium doped region and an intrinsic region. The n-type heavily doped region completely replaces the top silicon within a depth range. The n-type medium doped region and the intrinsic region The intrinsic region is arranged in the hollow area between the n-type heavily doped regions and the intrinsic region is located on the upper side of the n-type medium doped region. The shape of the silicon dioxide window layer matches the n-type heavily doped region and is correspondingly made on the upper side of the n-type heavily doped region. The lower outer edge of the long-wave absorption layer grows in the silicon dioxide window layer and completely covers the n-type medium doped region and the upper side of the intrinsic region. The n-electrode is made on the n-type medium doped region, and the p-electrode is made on the top of the long-wave absorption layer; the top of the long-wave absorption layer is provided with a p-type doped region, and the p-electrode is made on the p-type doped region, so as to realize wide spectrum detection of 300nm-2000nm.

2. The silicon-based wide spectrum detector array according to claim 1, characterized in that: The n-type heavily doped region is distributed in a rectangular shape on the outer edge of a single detector unit, the n-type medium doped region is distributed in a geometric shape in the hollow region inside the n-type heavily doped region, the lower side of the n-type medium doped region is located on the upper side of the silicon dioxide buried layer and the n-type medium doped region partially replaces the top silicon within a depth range, and the hollow region inside the n-type heavily doped region is all intrinsic region except the n-type medium doped region.

3. The silicon-based wide spectrum detector array according to claim 1, characterized in that: The invention also comprises an insulating medium layer, which is arranged on the outer sides of the silicon dioxide window layer and the long-wave absorption layer.

4. The silicon-based wide spectrum detector array according to claim 1, characterized in that: The bottom Si material layer and the long-wave absorption layer are staggered.

5. The silicon-based wide spectrum detector array according to claim 1, characterized in that: The material of the long-wave absorption layer is pure germanium, germanium-tin alloy or germanium-silicon alloy.

6. A method for preparing a silicon-based wide spectrum detector array according to any one of claims 1 to 5, characterized in that The following steps are involved: S1, respectively making an n-type heavily doped region and an n-type medium doped region on the top silicon layer, and the undoped region is the intrinsic region; S2, depositing silicon dioxide on the surface of the top silicon to form a silicon dioxide window layer, and opening windows on the silicon dioxide window layer corresponding to the n-type middle doped region and the region above the intrinsic region; S3, selectively epitaxially growing a long-wave absorption layer on the top silicon exposed in the window of the silicon dioxide window layer; S4, making a p-type doped region on the top of the long-wave absorption layer; S5, depositing an insulating dielectric layer on the long-wave absorption layer and the silicon dioxide window layer; S6. Making an n-electrode common to all detector units on the top silicon layer corresponding to the n-type heavily doped region, wherein the n-electrode is electrically connected to the n-type heavily doped region; S7, making an independent p-electrode on the p-type doping region of each detector unit, and the p-electrode is electrically connected to the p-type doping region; S8, annealing to form ohmic contact; S9, thinning the bottom Si material layer and removing the corresponding Si material layer below the long-wave absorption layer to complete the preparation.

7. The preparation method according to claim 6, characterized in that: In step S1, the thickness of the top silicon layer is greater than 200 nm, the thickness of the silicon dioxide buried layer is greater than 300 nm, and the crystal orientation of the top silicon layer is <001> direction, the conductivity type of the top silicon is p-type, the resistivity is 10 ohms / cm, the injection depth of the n-type heavily doped region is 0 to 340nm, and the doping concentration is greater than 1×10 19 cm -3 The ion implantation depth of the n-type doping region is 200-340 nm, and the doping concentration is greater than 1×10 18 cm -3 .

8. The preparation method according to claim 6, characterized in that: In step S2, silicon dioxide is deposited on the top silicon surface by an ion enhanced chemical vapor deposition system or a thermal oxidation method, and windows are opened on the silicon dioxide on the upper side of the n-type doped region and the intrinsic region by using a photoresist as a mask and a combination of dry and wet etching methods.

9. The preparation method according to claim 6, characterized in that: In the step S3, an ultra-high vacuum chemical vapor deposition system is used to epitaxially grow a long-wave absorption layer in the window of the silicon dioxide window layer.

10. The preparation method according to claim 6, characterized in that: In the step S8, the annealing temperature is 150-750°C.

11. The preparation method according to claim 6, characterized in that: In the step S9, a mechanical grinding process is used to thin the bottom Si material layer, and then a photoresist is used as a mask and dry etching is performed to remove the corresponding Si material layer below the long-wave absorption layer to complete the preparation.

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