Infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction and preparation method thereof

Abstract

The present invention discloses an infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction and a preparation method thereof, which mainly solves the problems of large dark current, small gain, and too high avalanche threshold voltage of existing avalanche photodetectors, and proposes a new infrared photodetector with low avalanche threshold voltage with separated absorption layer and multiplication layer. The photodetector uses macroscopically assembled graphene as an infrared light absorption layer and an epitaxial silicon layer as a carrier multiplication layer, and effectively suppresses noise current multiplication through the separation of the absorption multiplication layer, thereby realizing sensitive detection of weak light signals; under a large reverse bias, photogenerated carriers cross the potential barrier and collide with the silicon lattice in the depletion region to ionize, and excite exponentially multiplied carriers to contribute to the photocurrent, thereby realizing a large internal gain; the photodetector of the present invention can detect infrared spectra, solve the problem of low response of traditional Schottky barrier detectors to infrared light detection, and is conducive to the transmission of information in the communication band.

Description

Technical Field

[0001] The invention relates to an infrared avalanche photoelectric detector based on macroscopically assembled graphene / epitaxial silicon Schottky junction and a preparation method thereof, belonging to the technical field of photoelectric detection. Background Art

[0002] Infrared photodetectors have the advantages of strong penetration, long range, good anti-interference, and all-weather and all-day operation, and have been widely used in both military and civilian fields. Moreover, driven by military needs and the development of related technologies, infrared detection technology, as a high-tech technology, will be more widely used in the future and will have a more important position. Avalanche photodetectors have internal avalanche gain, high sensitivity, fast response, small size, low cost, easy integration, and can work at low temperatures. They show outstanding advantages in the fields of high-speed modulation and weak light signal detection. Traditional silicon-based detection devices cannot be well applied to infrared spectrum detection due to their bandgap defects. Therefore, it is necessary to find narrow bandgap materials compatible with silicon to improve the detection performance of the entire device.

[0003] As one of the representatives of single-atom layered two-dimensional materials, graphene has attracted extensive attention and research due to its characteristics of zero band gap, ultra-high carrier mobility, easy control of Fermi level, and easy formation of hot carriers. It is expected to be applied to the new infrared detection field of wide spectrum absorption, ultra-fast response, and high specific detection rate. Single-layer graphene is considered to be an emerging room temperature wide spectrum light detection material. Its van der Waals contact with semiconductors optimizes the heterojunction interface and suppresses dark current and device noise. Although single-layer graphene with a zero band gap structure has the advantage of wide spectrum absorption, the light absorption of only 2.3% is very weak, which limits the quantum conversion efficiency of graphene photodetectors. It is well known that the light absorption of graphene is directly related to the number of layers, which means that within a certain range, the thicker the graphene, the stronger its infrared spectrum absorption performance. Therefore, it is necessary to use macroscopically assembled multilayer graphene as the light absorption layer of infrared photodetectors.

[0004] In summary, high-performance avalanche photodetectors with fast response, high sensitivity and large gain at communication wavelengths depend not only on whether there is a thick and high-quality graphene film as a light absorption layer, but also on achieving low defect density at the graphene / silicon interface. Therefore, the dark current of the device is a very critical parameter, which affects the noise of the device, and large noise will interfere with the sensitive detection of weak light by the avalanche detection device. The Schottky junction with graphene as the light absorption layer and silicon as the photogenerated carrier multiplication layer effectively suppresses the multiplication of hot carriers, thereby improving the performance of the device and enhancing the accuracy and sensitivity of infrared spectrum detection. Summary of the invention

[0005] The purpose of the present invention is to address the shortcomings of existing avalanche photodetector devices and provide an infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction, which has a simple preparation process, low cost, high device responsiveness, large detection rate and internal gain, fast response speed, high photoelectric conversion efficiency and easy integration.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] According to the first aspect of the present specification, there is provided an infrared avalanche photodetector based on a macroscopically assembled graphene / epitaxial silicon Schottky junction, comprising: a bottom electrode, an n-type heavily doped silicon substrate, an epitaxial silicon layer, a dielectric isolation layer, a dielectric isolation layer window, a top electrode and a macroscopically assembled graphene film; wherein, the bottom electrode is covered on the lower surface of the n-type heavily doped silicon substrate, and an epitaxial silicon layer is grown on the upper surface; a dielectric isolation layer is grown on the upper surface of the epitaxial silicon layer, a top electrode is deposited on the upper surface of the dielectric isolation layer, a dielectric isolation layer window is opened in the top electrode and extends to the upper surface of the epitaxial silicon layer, so that the dielectric isolation layer has a concave structure, and the boundary of the dielectric isolation layer window is smaller than the boundary of the top electrode; the top electrode and the upper surface of the epitaxial silicon layer are covered with the macroscopically assembled graphene film.

[0008] Furthermore, the bottom electrode is a metal electrode, and the metal material is gold, silver, copper, aluminum, platinum, nickel-chromium alloy and gallium-indium alloy; the top electrode is a metal film electrode with a thickness of 10 to 100 nm, and the metal material is gold, aluminum, platinum, titanium-gold alloy, chromium-gold alloy and indium tin oxide.

[0009] Furthermore, the doping concentration of the n-type heavily doped silicon substrate is 10 18 ~10 20 cm -3 , resistivity is between 0.001 and 0.01Ω·cm, and thickness is 50 to 800μm.

[0010] Furthermore, the epitaxial silicon layer is made of intrinsic silicon or lightly doped n-type silicon, and the doping concentration of the lightly doped n-type silicon is 10 10 ~10 17 cm -3 , resistivity is between 1 and 5 kΩ·cm, and thickness is 0.1 to 10 μm.

[0011] Furthermore, the dielectric isolation layer material is silicon dioxide, silicon nitride, boron nitride, silicon oxynitride, aluminum oxide, or rutile titanium dioxide, and has a thickness of 10 to 500 nm.

[0012] Furthermore, the dielectric isolation layer window is circular or square in shape and has an area of ​​10 μm 2 ~4mm 2 .

[0013] Furthermore, the macroscopically assembled graphene film can be prepared by mechanical exfoliation, chemical vapor deposition or suction filtration sintering, and has a thickness of 5 to 60 nm.

[0014] Furthermore, the macroscopically assembled graphene film can be processed to present a micro-nano structure, and the micro-nano structure includes nano-strips, nano-gratings, and nano-concave shapes, which enhance the absorption and conversion of infrared light and improve the quantum conversion efficiency.

[0015] Furthermore, in the macroscopically assembled graphene film / epitaxial silicon layer structure, the macroscopically assembled graphene film serves as an infrared light absorption layer, the epitaxial silicon layer serves as a carrier multiplication layer, and the infrared detection band is 1.1 to 16 μm.

[0016] According to a second aspect of the present specification, there is provided a method for preparing the above-mentioned infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction, the method comprising the following steps:

[0017] (1) cleaning the surface of an n-type heavily doped silicon substrate by placing it in acetone, isopropanol, and deionized water solution for ultrasonic cleaning, and then taking it out and blowing it dry with nitrogen;

[0018] (2) growing an epitaxial silicon layer on the upper surface of the cleaned n-type heavily doped silicon substrate by vapor phase epitaxy. Other growth methods include: liquid phase epitaxy, solid phase epitaxy or molecular beam epitaxy;

[0019] (3) growing a dielectric isolation layer on the upper surface of the epitaxial silicon layer by plasma enhanced chemical vapor deposition, other growth methods also include: high temperature thermal oxidation method, magnetron sputtering, the thickness of the dielectric isolation layer is 10 to 500 nm;

[0020] (4) photolithography of a top electrode pattern on the surface of the dielectric isolation layer, and then sequentially depositing a titanium adhesion layer with a thickness of 5 to 10 nm and a gold electrode with a thickness of 40 to 60 nm by magnetron sputtering;

[0021] (5) photolithography a dielectric isolation layer window pattern in the dielectric isolation layer within the shape of the top electrode, and then etching away the isolation dielectric using a buffered oxide etching solution composed of water, HF and NH4F to form a concave structure, exposing the epitaxial silicon layer in a specific area within the dielectric isolation layer window;

[0022] (6) preparing a redox graphene film on an AAO nano-alumina template by a filtration method, and forming a macroscopic assembled graphene film after high temperature sintering at a temperature of 1000 to 3000°C;

[0023] (7) covering the upper surfaces of the dielectric isolation layer, the top electrode and the epitaxial silicon layer with a macroscopically assembled graphene film; wherein the transfer method of the macroscopically assembled graphene film is as follows: dropping a drop of a mixture of ethanol: deionized water = 1:5 (volume ratio) at the upper surface position of the top electrode and the epitaxial silicon layer, then tearing off a small piece of the macroscopically assembled graphene film with tweezers, and spreading it evenly on the mixed liquid ball drop, and then blowing away the mixed liquid with a small flux of argon gas, so that the macroscopically assembled graphene film is evenly spread on the dielectric isolation layer, the top electrode and the epitaxial silicon layer, and is in close contact with them;

[0024] (8) etching the excess macroscopically assembled graphene film on the dielectric isolation layer, leaving only the macroscopically assembled graphene film in contact with the top electrode and the upper surface of the epitaxial silicon layer; wherein the etching method comprises: using a photoresist to protect the macroscopically assembled graphene film in contact with the top electrode and the upper surface of the epitaxial silicon layer, and then performing plasma etching on the macroscopically assembled graphene film on the dielectric isolation layer by using an inductively coupled plasma spectrometer to remove the excess macroscopically assembled graphene film other than the top electrode;

[0025] (9) performing high temperature annealing on the entire macro-assembled graphene / epitaxial silicon vertical structure to eliminate the defect state at the interface between the macro-assembled graphene film and the epitaxial silicon layer, so that the macro-assembled graphene film is in better and closer contact with the top electrode and the epitaxial silicon layer; annealing conditions: temperature 400-500° C., time 5-10 min;

[0026] (10) A gold electrode is coated on the bottom of the n-type heavily doped silicon substrate by electron beam evaporation to form a good ohmic contact with the n-type heavily doped silicon substrate.

[0027] The present invention has the following beneficial effects:

[0028] 1. Because graphene is an ultra-thin two-dimensional material with zero bandgap, it has the optical property of wide-spectrum absorption and has good absorption effect on any wavelength of light in the ultraviolet-visible-infrared wide spectrum. This is a major advantage of graphene film for photoelectric detection; and its absorption intensity can be enhanced by increasing the thickness of graphene, expanding the absorption of 2.3% of single-layer graphene in the infrared spectrum to more than 45% of macro-assembled graphene, greatly improving the light absorption, thereby improving the photoelectric conversion efficiency of macro-assembled graphene / epitaxial silicon photodetection devices.

[0029] 2. The infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction realizes the separation of the light absorption layer and the carrier multiplication layer. Since the bandgap width of silicon is 1.12eV, the corresponding light absorption cutoff wavelength is around 1.1μm. For infrared spectra greater than 1.1μm, the macroscopically assembled graphene plays the role of a light absorption layer in the entire infrared avalanche photodetector device, while the epitaxial silicon wafer acts as a carrier multiplication layer, which solves the problem of hot carrier avalanche multiplication caused by the light absorption layer and the multiplication layer being in the same area, greatly improving the sensitive detection of weak light signals.

[0030] 3. Macroscopically assembled graphene and epitaxial silicon form a Schottky junction, which has a rectifying effect, which not only reduces the noise current of the avalanche photodetector, but also accelerates the separation of photogenerated electron-hole pairs and inhibits the recombination of the two, thereby improving the quantum efficiency in the infrared light spectrum.

[0031] 4. Under the action of an externally increased reverse bias, the depletion region of the epitaxial silicon layer becomes wider, the region where carrier multiplication occurs is also widened, and the built-in electric field is also enhanced, which greatly improves the efficiency of avalanche multiplication and reduces the avalanche start voltage.

[0032] 5. Selecting n-type heavily doped silicon as the substrate can, on the one hand, solve the problem of ohmic contact between semiconductor and metal and form a good ohmic contact with the back electrode; on the other hand, it accelerates the mobility of carriers and improves the response speed of avalanche photodetection devices.

[0033] 6. The infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction of the present invention uses silicon as the basic material, has low cost, simple preparation process, and is easily compatible with existing semiconductor standard processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The schematic diagram of the structure of the infrared avalanche photodetector based on the macroscopically assembled graphene / epitaxial silicon Schottky junction of the present invention includes a bottom electrode 1, an n-type heavily doped silicon substrate 2, an epitaxial silicon layer 3, a dielectric isolation layer 4, a dielectric isolation layer window 5, a top electrode 6, and a macroscopically assembled graphene film 7;

[0035] Figure 2 This is a diagram of the avalanche multiplication mechanism of the infrared avalanche photodetector based on the macroscopically assembled graphene / epitaxial silicon Schottky junction of the present invention. The macroscopically assembled graphene film absorbs infrared photons and converts them into electron-hole pairs, which are separated under the action of the built-in electric field. The electrons cross the potential barrier and collide with the epitaxial silicon layer and multiply exponentially, contributing to the entire circuit.

[0036] Figure 3 The infrared avalanche photodetector prepared in the embodiment of the present invention exhibits a positive temperature coefficient in the avalanche multiplication phenomenon in dark environments at different temperatures;

[0037] Figure 4 The infrared avalanche photodetector prepared in the embodiment of the present invention works at room temperature at a bias voltage of 0 to -25V, a wavelength of 1550nm, and an optical power density of 0.11W / mm 2 The optical response curve of the device with infrared light on and off and the curve of its internal gain changing with reverse bias voltage. DETAILED DESCRIPTION

[0038] The working principle of an infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction provided by the present invention is as follows:

[0039] like Figure 2 As shown, the macro-assembled graphene contacts the epitaxial silicon layer to form a Schottky junction, and the built-in electric field is directed from the silicon base to the graphene. When infrared light with a wavelength greater than 1.1μm is irradiated onto the macro-assembled graphene, since the bandgap width of silicon is 1.12eV and the cut-off wavelength is less than 1.1μm, the macro-assembled graphene dominates the light absorption, absorbing photons and generating electron-hole pairs in the macro-assembled graphene. Under the action of the built-in electric field, the electron-hole pairs are separated, and the electrons cross the potential barrier to reach the conduction band of the epitaxial silicon. And under the action of large reverse bias, the depletion region widens, the built-in electric field strength increases, the photogenerated electrons gain greater energy, and thus have high kinetic energy, which collides and ionizes with electrons near the silicon lattice in the depletion region, exciting new free electrons. The electrons continue to collide and ionize, and then exponentially multiply free electrons are generated. Eventually, the holes flow to the macroscopically assembled graphene and are collected by the top electrode, and the electrons flow to the n-type heavily doped silicon substrate and are collected by the bottom electrode, contributing to the photogenerated current.

[0040] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0041] like Figure 1 As shown, the infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction provided in this embodiment includes: a bottom electrode 1, an n-type heavily doped silicon substrate 2, an epitaxial silicon layer 3, a dielectric isolation layer 4, a dielectric isolation layer window 5, a top electrode 6, and a macroscopically assembled graphene film 7; wherein, the bottom surface of the n-type heavily doped silicon substrate 2 is covered with the bottom electrode 1, and an epitaxial silicon layer 3 is grown on the upper surface; a dielectric isolation layer 4 is grown on the upper surface of the epitaxial silicon layer 3, and a top electrode 6 is deposited on the upper surface of the dielectric isolation layer 4, and a dielectric isolation layer window 5 is opened in the top electrode 6, so that the silicon dioxide isolation layer 4 has a concave structure, and the surface of the epitaxial silicon layer 3 in a specific area is exposed, and the boundary of the dielectric isolation layer window 5 is smaller than the boundary of the top electrode 6; the top surface of the top electrode 6 and the epitaxial silicon layer 3 is covered with the macroscopically assembled graphene film 7.

[0042] In some other embodiments: the bottom electrode 1 is a metal electrode, and the metal material is gold, silver, copper, aluminum, platinum, nickel-chromium alloy and gallium-indium alloy. The top electrode 6 is a metal film electrode with a thickness of 10 to 100 nm, and the metal material is gold, aluminum, platinum, titanium-gold alloy, chromium-gold alloy and indium tin oxide. The doping concentration of the n-type heavily doped silicon substrate 2 is 10 18 ~10 20 cm -3 , 10 can be selected 19 cm -3 The resistivity is between 0.001 and 0.01 Ω·cm, and the thickness is between 50 and 800 μm. The epitaxial silicon layer 3 is made of intrinsic silicon or lightly doped n-type silicon, and the doping concentration of lightly doped n-type silicon is 10 10 ~10 17 cm -3 , the resistivity is between 1 and 5 kΩ·cm, and the thickness is 0.1 to 10 μm. The dielectric isolation layer 4 is made of silicon dioxide, silicon nitride, boron nitride, silicon oxynitride, aluminum oxide, rutile titanium dioxide, and has a thickness of 10 to 500 nm. The dielectric isolation layer 5 is circular or square in shape, with an area of ​​10 μm 2 ~4mm 2 The macroscopically assembled graphene film 7 is prepared by mechanical exfoliation, chemical vapor deposition or suction sintering, and has a thickness of 5 to 60 nm. The macroscopically assembled graphene film 7 can be processed to present a micro-nano structure, which includes nano-strips, nano-gratings, nano-concave shapes, etc., to enhance the absorption and conversion of infrared light and improve quantum conversion efficiency.

[0043] The present invention also provides an embodiment of a method for preparing the above-mentioned infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction, comprising the following steps:

[0044] (1) The n-type heavily doped silicon substrate 2 is subjected to surface cleaning treatment by sequentially placing it in acetone, isopropanol, and deionized water solutions for ultrasonic cleaning for 5 minutes, and then taken out and blown dry with nitrogen;

[0045] (2) growing an epitaxial silicon layer 3 on the upper surface of the cleaned n-type heavily doped silicon substrate 2 by vapor phase epitaxy, using precursors SiCl4 and H2, with a SiCl4 mole fraction of 0.1, an H2 flow rate of 1 L / min, a deposition temperature of 1270°C, and a growth rate of 1 μm / min;

[0046] (3) growing a silicon dioxide isolation layer 4 on the upper surface of the epitaxial silicon layer 3 by plasma enhanced chemical vapor deposition, with a thickness of 300 nm, controlling the precursor gas and flux: SiH4 (40 sccm) and N2O (120 sccm), growth temperature 350°C, deposition power 100 W, deposition rate 1 nm / s;

[0047] (4) A top electrode pattern was photolithographically formed on the surface of the silicon dioxide isolation layer 4, and then a titanium adhesion layer with a thickness of 10 nm and a gold electrode with a thickness of 60 nm were successively deposited by magnetron sputtering, with sputtering powers of 100 W and 200 W, respectively, and sputtering rates of 100 nm / min and 1 nm / s, respectively;

[0048] (5) Photolithography a silicon dioxide window 5 pattern on the silicon dioxide isolation layer 4 in the shape of the top electrode 6, post-baking on a heating platform at 105° C. for 5 min, and then etching away the silicon dioxide to form a concave structure using a buffered oxide etchant composed of water, HF and NH4F, exposing the epitaxial silicon layer 3 in a specific area within the silicon dioxide window 5, wherein the volume ratio of H2O:NH4F:HF=10:6:3, and the etching rate is about 100 nm / min;

[0049] (6) adding graphene oxide powder to deionized water and ultrasonically oscillating for 1 h, taking the upper clear liquid, preparing a redox graphene film on the AAO nano-alumina template by suction filtration, and forming a macroscopic assembled graphene film 7 after high-temperature sintering at 2000°C;

[0050] (7) covering the upper surfaces of the silicon dioxide isolation layer 4, the top electrode 6 and the epitaxial silicon layer 3 with a macroscopically assembled graphene film 7; wherein the transfer method of the macroscopically assembled graphene film 7 is as follows: dropping a drop of a mixture of ethanol and deionized water at the upper surface of the top electrode 6 and the epitaxial silicon layer 3, with a volume ratio of 1:5, then using tweezers to tear off a small piece of the macroscopically assembled graphene film 7, and spreading it evenly on the mixed liquid ball drop, and then using a small flux of argon gas to blow away the mixed liquid, so that the macroscopically assembled graphene film 7 is evenly spread on the silicon dioxide isolation layer 4, the top electrode 6 and the epitaxial silicon layer 3, and is in close contact with them;

[0051] (8) etching the excess macroscopically assembled graphene film on the silicon dioxide isolation layer 4, leaving only the macroscopically assembled graphene film 7 in contact with the top electrode 6 and the upper surface of the epitaxial silicon layer 3; wherein the etching method is: using a photoresist to protect the macroscopically assembled graphene film 7 in contact with the top electrode 6 and the upper surface of the epitaxial silicon layer 3, and then plasma etching the macroscopically assembled graphene film on the silicon dioxide isolation layer 4 by an inductively coupled plasma spectrometer to remove the excess macroscopically assembled graphene film other than the top electrode 6, the etching power is 70W, and the etching time is 200s;

[0052] (9) performing high temperature annealing on the entire macro-assembled graphene / epitaxial silicon vertical structure to eliminate the defect state at the interface between the macro-assembled graphene 7 and the epitaxial silicon wafer 3, so that the macro-assembled graphene film 7 is in better and closer contact with the top electrode 6 and the epitaxial silicon layer 3; annealing conditions: temperature 450° C., time 5 min;

[0053] (10) A gold bottom electrode 1 is covered at the bottom of the n-type heavily doped silicon substrate 2 by electron beam evaporation with a thickness of 10 nm to form a good ohmic contact with the n-type heavily doped silicon substrate 2.

[0054] A large reverse bias is applied to the infrared avalanche photodetector based on the macro-assembled graphene / epitaxial silicon Schottky junction, and the photogenerated electrons generated in the macro-assembled graphene film 7 produce an avalanche multiplication effect in the epitaxial silicon layer 3 to achieve internal gain. The negative electrode of the source-meter applied voltage is connected to the bottom electrode 1 of the device, and the positive electrode is connected to the top electrode 6 of the device.

[0055] The infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction prepared in this embodiment works in a dark environment at a temperature of 280-350K. The avalanche threshold voltage changes with temperature as shown in FIG. Figure 3 As shown. As can be seen from the figure, as the temperature increases, the avalanche threshold voltage increases. This is because: as the temperature increases, the excitation phenomenon of the epitaxial silicon layer itself will be strengthened, and those valence electrons that have not been intrinsically excited to become free electrons will also vibrate spontaneously in the lattice. The vibration of these valence electrons will also lead to an increase in the required space, and the carriers that dominate the avalanche breakdown are minority carriers. Its movement in the depletion region requires a process of energy accumulation. As long as the energy is large enough, an avalanche phenomenon will occur, and this accumulation process requires an acceleration and a distance; now these valence electrons have a larger space, so the minority carriers are easy to collide with these valence electrons during the acceleration process before the energy reaches the point where the covalent bond can be destroyed, but the energy is not enough to knock the valence electrons out of the lattice, so in this case, an avalanche cannot occur. Only by increasing the intensity of the electric field and obtaining a greater acceleration can a greater energy be obtained at a shorter distance to form an avalanche multiplication, so the temperature coefficient of the avalanche phenomenon is positive.

[0056] The infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction prepared in this embodiment has dark current and photocurrent and internal gain curves with reverse bias under 0 to -25V bias, dark environment and 1550nm infrared light irradiation. Figure 4 As shown. The negative pole of the source meter external voltage is connected to the bottom electrode 1 of the device, and the positive pole is connected to the top electrode 6 of the device. Figure 4 It can be seen that the current of the prepared avalanche device is very small in a dark environment; when the wavelength is 1550nm and the optical power density is 0.11W / mm 2 When the device is operated at -25V, the optical response is 2.51mA / W and the internal gain is ~9000, which proves that the infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction has good photodetection performance.

[0057] The above is only a preferred embodiment of the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. An infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction, characterized in that: include: A bottom electrode (1), an n-type heavily doped silicon substrate (2), an epitaxial silicon layer (3), a dielectric isolation layer (4), a dielectric isolation layer window (5), a top electrode (6) and a macroscopically assembled graphene film (7); wherein the bottom surface of the n-type heavily doped silicon substrate (2) is covered with the bottom electrode (1), and an epitaxial silicon layer (3) is grown on the top surface, wherein the material of the epitaxial silicon layer (3) is intrinsic silicon or lightly doped n-type silicon, and the doping concentration of the lightly doped n-type silicon is 10 10 ~10 17 cm -3 , the resistivity is between 1 and 5 kW×cm, and the thickness is 0.1 to 10 mm; a dielectric isolation layer (4) is grown on the upper surface of the epitaxial silicon layer (3), a top electrode (6) is deposited on the upper surface of the dielectric isolation layer (4), a dielectric isolation layer window (5) is opened in the top electrode (6) and penetrates to the upper surface of the epitaxial silicon layer (3), so that the dielectric isolation layer (4) has a concave structure, and the boundary of the dielectric isolation layer window (5) is smaller than the boundary of the top electrode (6); a macroscopically assembled graphene film (7) is covered on the upper surface of the top electrode (6) and the epitaxial silicon layer (3), and in the macroscopically assembled graphene film / epitaxial silicon layer structure, the macroscopically assembled graphene film (7) serves as an infrared light absorption layer, and the epitaxial silicon layer (3) serves as a carrier multiplication layer, and the infrared detection band is 1.1 to 16 mm.

2. An infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction according to claim 1, characterized in that: The bottom electrode (1) is a metal electrode, and the metal material is gold, silver, copper, aluminum, platinum, nickel-chromium alloy and gallium-indium alloy; the top electrode (6) is a metal film electrode, with a thickness of 10-100 nm, and the metal material is gold, aluminum, platinum, titanium-gold alloy, chromium-gold alloy and indium tin oxide.

3. An infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction according to claim 1, characterized in that: The doping concentration of the n-type heavily doped silicon substrate (2) is 10 18 ~10 20 cm -3 , resistivity is between 0.001~0.01 W×cm, and thickness is 50~800mm.

4. The infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction according to claim 1, characterized in that: The dielectric isolation layer (4) is made of silicon dioxide, silicon nitride, boron nitride, silicon oxynitride, aluminum oxide, or rutile titanium dioxide, and has a thickness of 10 to 500 nm.

5. The infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction according to claim 1, characterized in that: The dielectric isolation layer window (5) is circular or square in shape and has an area of ​​10 mm 2 ~4mm 2 .

6. The infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction according to claim 1, characterized in that: The macroscopically assembled graphene film (7) is prepared by mechanical exfoliation, chemical vapor deposition or suction filtration sintering, and has a thickness of 5 to 60 nm.

7. An infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction according to claim 1, characterized in that: The macroscopically assembled graphene film (7) is processed to present a micro-nano structure, which includes nano-strips, nano-gratings, and nano-concave shapes, thereby enhancing the absorption and conversion of infrared light and improving quantum conversion efficiency.

8. A method for preparing an infrared avalanche photodetector based on macroscopically assembled graphene / epitaxial silicon Schottky junction as described in any one of claims 1 to 7, characterized in that: The following steps are involved: (1) performing surface cleaning treatment on the n-type heavily doped silicon substrate (2), placing it in acetone, isopropanol, and deionized water solution for ultrasonic cleaning in sequence, and then taking it out and blowing it dry with nitrogen; (2) growing an epitaxial silicon layer (3) on the upper surface of the cleaned n-type heavily doped silicon substrate (2); (3) growing a dielectric isolation layer (4) on the upper surface of the epitaxial silicon layer (3), wherein the dielectric isolation layer (4) has a thickness of 10 to 500 nm; (4) photolithography a top electrode (6) pattern on the surface of the dielectric isolation layer (4), and then sequentially depositing a titanium adhesion layer with a thickness of 5 to 10 nm and a gold electrode with a thickness of 40 to 60 nm by magnetron sputtering; (5) photolithography a dielectric isolation layer window (5) pattern on the dielectric isolation layer (4) in the shape of the top electrode (6), and then etching away the isolation dielectric with a buffered oxide etching solution to form a concave structure, thereby exposing the epitaxial silicon layer (3) in a specific area within the dielectric isolation layer window (5); (6) Prepare redox graphene film on AAO nano-alumina template by filtration method, and form macroscopic assembled graphene film after high temperature sintering (7); (7) covering the upper surfaces of the dielectric isolation layer (4), the top electrode (6) and the epitaxial silicon layer (3) with a macroscopically assembled graphene film (7); the transfer method of the macroscopically assembled graphene film (7) is as follows: dropping a drop of a mixture of ethanol and deionized water on the upper surfaces of the top electrode (6) and the epitaxial silicon layer (3), then using tweezers to tear off a small piece of the macroscopically assembled graphene film (7), and spreading it evenly on the mixed liquid ball drop, and then using argon gas to blow away the mixed liquid, so that the macroscopically assembled graphene film (7) is evenly spread on the dielectric isolation layer (4), the top electrode (6) and the epitaxial silicon layer (3), and is in close contact with them; (8) etching the excess macroscopically assembled graphene film (7) on the dielectric isolation layer (4) to leave only the macroscopically assembled graphene film (7) in contact with the top electrode (6) and the upper surface of the epitaxial silicon layer (3); the etching method is: using a photoresist to protect the macroscopically assembled graphene film (7) in contact with the top electrode (6) and the upper surface of the epitaxial silicon layer (3), and then plasma etching the macroscopically assembled graphene film (7) on the dielectric isolation layer (4) by using an inductively coupled plasma spectrometer to remove the excess macroscopically assembled graphene film (7) other than the top electrode; (9) performing high temperature annealing on the entire macro-assembled graphene / epitaxial silicon vertical structure to eliminate the defect state at the interface between the macro-assembled graphene film (7) and the epitaxial silicon layer (3), so that the macro-assembled graphene film (7) is in better and closer contact with the top electrode (6) and the epitaxial silicon layer (3); annealing conditions: temperature 400-500° C., time 5-10 min; (10) A gold electrode is covered on the bottom of the n-type heavily doped silicon substrate (2) by electron beam evaporation to form a good ohmic contact with the n-type heavily doped silicon substrate (2).

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