CN111341862B - Solar blind ultraviolet avalanche photodetector and preparation method thereof - Google Patents

Solar blind ultraviolet avalanche photodetector and preparation method thereof Download PDF

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CN111341862B
CN111341862B CN202010169162.3A CN202010169162A CN111341862B CN 111341862 B CN111341862 B CN 111341862B CN 202010169162 A CN202010169162 A CN 202010169162A CN 111341862 B CN111341862 B CN 111341862B
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CN111341862A (en
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余晨辉
李林
陈红富
徐腾飞
罗曼
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Nantong University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
    • H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by at least one potential-jump barrier or surface barrier, e.g. phototransistors
    • H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
    • H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier
    • H01L31/107—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier the potential barrier working in avalanche mode, e.g. avalanche photodiode
    • H01L31/1075—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier the potential barrier working in avalanche mode, e.g. avalanche photodiode in which the active layers, e.g. absorption or multiplication layers, form an heterostructure, e.g. SAM structure
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    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
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    • H—ELECTRICITY
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
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Abstract

The invention discloses a solar blind ultraviolet avalanche photodetector andthe preparation method comprises the steps that the structure of the photoelectric detector sequentially comprises an AlN template layer, an AlN buffer layer and n-type Al from bottom to topx1Ga1‑x1N-layer, i-type Alx2Ga1‑x2N-absorption layer, N-type GeS separation layer, i-type Alx3Ga1‑x3An N-multiplication layer and a p-type GaN layer; the n-type Alx1Ga1‑ x1An N-type ohmic electrode is led out of the N layer; a p-type ohmic electrode is led out of the p-type GaN layer; the n-type GeS separation layer is respectively connected with the i-type Alx2Ga1‑x2N absorption layer and i-type Alx3Ga1‑x3The N-fold multiplication layer is formed by combining Van der Waals bonding. The n-type separation layer adopts the two-dimensional material GeS to replace the three-dimensional material AlGaN to be bonded with the upper and lower i-type AlGaN layers through Van der Waals force instead of a chemical epitaxial growth method, so that the problems of device breakdown in advance and polarization charge generation at an interface in the prior art are solved, and the response speed of the avalanche photodetector is improved.

Description

Solar blind ultraviolet avalanche photodetector and preparation method thereof
Technical Field
The invention relates to a photoelectric detector, in particular to a solar blind ultraviolet avalanche photoelectric detector and a preparation method thereof.
Background
In the electromagnetic spectrum, ultraviolet rays having wavelengths in the 200nm to 280nm band are called solar shadow regions. The solar blind band is not interfered by any other light in the atmosphere and cannot be transmitted to the atmosphere from the earth surface. The method is equivalent to forming a natural shielding cover by using a detection system of a solar blind waveband on the ground surface, and the photoelectric detection technology of the solar blind waveband has the characteristics of obvious target characteristics, strong anti-interference capability, good selectivity and the like, and shows incomparable superiority.
The multiplication absorption separation type (SAM) avalanche photodetector adopts a p-i1 (multiplication layer) -n1 (separation layer) -i2 (absorption layer) -n2 structure to effectively separate a light absorption layer from an avalanche multiplication layer, ensures the complete absorption of incident light, improves the quantum efficiency and spectral response of an avalanche diode, and reduces the reverse leakage current and noise equivalent power of the device. However, the separation layer n1 is formed between the upper and lower layersWhen the multiplication layer i1 and the absorption layer i2 are subjected to epitaxial growth by using an MOCVD method, a series of problems can be caused, for example, a large number of defects exist at an interface, and bound electrons influence current, so that the device breaks down in advance; failure to relax the stress at the interface results in the generation of polarization charges. Moreover, the mobility of AlGaN used for the separation layer n1 varies with Al composition, and the electron mobility reaches up to 480cm2V-1s-1The highest hole mobility can only reach 20cm2V-1s-1This results in insufficient conductivity and response speed.
A new material growth technology, van der waals bonding, has emerged today with many advantages over the commonly used heterogeneous material integration technology. Current methods of heterogeneous material integration typically rely on chemical epitaxial growth (CVD) or Physical Vapor Deposition (PVD). Such integration relies on one-to-one chemical bonding and is generally limited to materials with highly similar lattice symmetries and lattice constants, requiring similar processing conditions. Van der waals bonding technology has also received increasing attention in the industry as it provides another method of bond-free integration that is not limited by crystal lattice and process constraints. In principle, this keyless integration approach is not limited to a particular material size, allows highly different materials to be stacked layer by layer, and is generally applicable to materials having different crystal structures, electronic properties, or material sizes without requiring lattice matching and process compatibility. We will therefore innovatively apply this technique to the preparation of device isolation layers.
In recent years, photodetectors based on two-dimensional materials and their heterostructures have attracted great research interest. As one of the most competitive materials for designing photodetectors, two-dimensional materials have proven to have excellent properties including a wide detection band covering wavelengths from ultraviolet to terahertz frequencies, ultra-high photoresponsiveness, polarization-sensitive light detection, high-speed light response, high spatial resolution imaging, and the like, so that photodetectors based on two-dimensional materials have achieved many impressive achievements. Atoms of a two-dimensional material are arranged on a plane by tight covalent bonds or ionic bonds to form one atomic layer, and these atomic thin layers are bonded together in a three-dimensional direction perpendicular to the two-dimensional plane by weak van der waals force interactions. Weak interlayer interactions make it possible to exfoliate bulk crystals into isolated two-dimensional flakes or even thin layers of individual atoms. Here, we innovatively bond the two-dimensional material and the three-dimensional material together by using van der waals bonding technology to prepare a special two-dimensional material isolation layer, thereby solving a series of problems of using the three-dimensional material AlGaN material as the isolation layer.
Disclosure of Invention
The invention aims to provide a solar-blind ultraviolet avalanche photodetector and a preparation method thereof, which solve the problems of device breakdown in advance and polarization charge generation at an interface in the prior art and improve the response speed of the avalanche photodetector.
The technical scheme for realizing the purpose of the invention is as follows:
a solar blind ultraviolet avalanche photodetector comprises an AlN template layer, an AlN buffer layer and n-type Al sequentially arranged from bottom to topx1Ga1-x1N-layer, i-type Alx2Ga1-x2N-absorption layer, N-type GeS separation layer, i-type Alx3Ga1-x3An N-multiplication layer and a p-type GaN layer; an n-type ohmic electrode is led out of the n-type Alx1Ga1-x1N layer; a p-type ohmic electrode is led out of the p-type GaN layer; the n-type GeS separation layer is respectively connected with the i-type Alx2Ga1-x2N absorption layer and i-type Alx3Ga1-x3The N-fold multiplication layer is formed by combining Van der Waals bonding.
Further, the AlN template layer has a thickness of 500 nm; the AlN buffer layer is 100-300 nm thick; the n-type Alx1Ga1-x1The thickness of the N layer is 100-300 nm; the i-type Alx2Ga1-x2The thickness of the N absorption layer is 150-220 nm; the thickness of the n-type GeS separation layer is 1.2-1.8 nm; the i-type Alx3Ga1-x3The thickness of the N multiplication layer is 150-200 nm; the thickness of the p-type GaN layer is 10-300 nm.
Further, the number of layers of the n-type GeS separation layer is set to be two.
Further, the thickness of each n-type GeS separation layer is 0.6 nm.
Further, the AlN template layer adopts a sapphire template substrate.
Further, the n-type ohmic electrode is a Ti/Al/Ni/Au alloy electrode.
Further, the p-type ohmic electrode is a Ni/Au alloy electrode;
a preparation method of a solar blind ultraviolet avalanche photodetector is characterized by comprising the following steps:
s1: manufacturing a first module, wherein the first module sequentially comprises an AlN template layer, an AlN buffer layer and n-type Al from bottom to topx1Ga1-x1N layer and i type Alx2Ga1-x2An N absorption layer;
s2: manufacturing a second module, wherein the second module sequentially comprises an AlN template layer, an AlN buffer layer, an i-type Alx3Ga1-x3N layer and a p-type GaN layer from bottom to top;
s3: manufacturing a module III, wherein the module III comprises a module III substrate and an n-type GeS separation layer;
s4: stripping off the AlN template layer and the AlN buffer layer of the second module to obtain a combination of an i-type Alx3Ga1-x3N layer and a p-type GaN layer;
s5: combining all layers from bottom to top to obtain the I-type Al of the module Ix2Ga1-x2I-type Al of N absorption layer and module IIx3Ga1-x3The N multiplication layers are processed by an ex-situ method, the N-type GeS separation layer of the module III is peeled off from the module III substrate and is respectively bonded with the i-type Al of the module I by adopting the Van der Waals force bonding technologyx2Ga1-x2I-type Al of N absorption layer and module IIx3Ga1-x3Combining the N multiplication layers;
s6: etching the p-type GaN layer of a part of region from the upper surface to the upper surface of the n-type Alx1Ga1-x1N layer to form a table top, and performing purification treatment on the etched sample surface;
s7: in n-type Alx1Ga1-x1Evaporating an N-type ohmic electrode on the N-layer table board, and annealing the N-type ohmic electrode after evaporation;
s8: and evaporating the p-type ohmic electrode on the p-type GaN layer, and annealing the p-type ohmic electrode after evaporation.
Further, the manufacturing method of the module I comprises the following steps:
s11: cleaning the sapphire substrate as a module-substrate in NH3Nitriding the first substrate of the module under the atmosphere, and forming an AlN template layer on the first substrate of the module;
s12: growing an n-type AlN buffer layer on the AlN template layer of the module I;
s13: growing a layer of n-type Al on the AlN buffer layer of the module Ix1Ga1-x1N layers;
s14: in n-type Alx1Ga1-x1Growing a layer of i-type Al on the N layerx2Ga1-x2An N absorption layer;
further, the manufacturing method of the second module comprises the following steps:
s21: cleaning the sapphire substrate as the second substrate of the module at NH3Nitriding the second substrate of the module under the atmosphere, and forming an AlN template layer on the second substrate of the module;
s22: growing an n-type AlN buffer layer on the AlN template layer of the module II;
s23: growing an i-type Alx3Ga1-x3N layer on the AlN buffer layer of the module II;
s24: in type i Alx3Ga1-x3Growing a p-type GaN layer on the N multiplication layer;
further, the growing method of the module I and the module II adopts a Metal Organic Compound Vapor Deposition (MOCVD) method for growing.
Further, the preparation method of the module III adopts a chemical vapor deposition method to synthesize a GeS bulk thin sheet, and mechanically peels the GeS bulk thin sheet onto a module III substrate through a transparent adhesive tape, wherein the module III substrate is a Ni film, and the preparation method specifically comprises the following steps:
s31: placing the quartz boat filled with the GeS powder in the center of a quartz tube of a tube furnace;
s32: ultrasonically cleaning the Si substrate and drying;
s33: placing the Si substrate at a position 12-15cm below the center of the tube furnace;
s34: evacuating the quartz tube to a basic pressure of 80-100 mTorr, flushing with high-purity Ar gas, and introducing Ar gas until the pressure is kept at 20-40 Torr;
s35: after the pressure is stable, heating the tube furnace to 400-500 ℃, and depositing for 1-10 min when the deposition temperature of the substrate reaches 290-330 ℃;
s36: after deposition is finished, naturally cooling the tube furnace to room temperature to prepare GeS nano sheets;
s72: mixing the GeS nanosheets with purified water, and stirring to obtain a GeS mixed solution;
s73: adding a surfactant NMP into the GeS mixed solution, and shearing and stripping to obtain a GeS solution;
s74: centrifuging the GeS solution obtained by shearing and stripping, pouring the solution into a culture dish, and drying the culture dish in a vacuum drying oven to obtain a GeS product;
s75: growing a GeS layer on the sapphire wafer by using an MOCVD method;
s76: depositing a Ni film on the GeS layer, adhering a heat-insulating adhesive tape on the Ni film as a treating agent, and tearing the adhesive tape to separate the weakest GeS-sapphire interface, so that the whole GeS film is released from the substrate;
s77: depositing a layer of Ni film at the bottom of the GeS film, applying a torque on the top Ni film to start the spalling mode fracture, guiding downward cracks, and repeatedly stripping; the Ni/GeS layer separates after spalling, and the underlying Ni film has a strong adhesion to the GeS monolayer, leaving the GeS monolayer on the underlying Ni film.
Further, the step S4 is to strip off the AlN template layer and the AlN buffer layer of the module II by using a mechanical stripping method.
Further, the ex-situ processing in S5 includes the following steps:
s51: immersing the sample in an HF acid solution for 3 minutes;
s52: taking out, immediately drying with N2, and placing in a vacuum system with base pressure not more than 5 × 10-9Torr, reducing the exposure of indoor air;
s53: under the condition of extra-high voltage, the base pressure is less than 5 multiplied by 10-9Torr, the sample is heated to the desired temperature using a hot wire at a rate of 75 deg.C/min for a thermal desorption process and held for 15min before cooling.
By adopting the technical scheme, the invention has the following beneficial effects:
(1) the n-type separation layer of the avalanche photodetector adopts the two-dimensional material GeS to replace the three-dimensional material AlGaN and is bonded with the upper and lower i-type AlGaN layers by Van der Waals force instead of a chemical epitaxial growth method, the influence of lattice matching is avoided, a large number of defects at the interface can not exist to cause the influence of bound electrons on current, and therefore the device can not be broken down in advance.
(2) The invention adopts Van der Waals force bonding technology to combine the n-type GeS separation layer and the upper and lower i-type AlGaN layers, and the device adopting the chemical epitaxial growth method is influenced by the stress and the tension of the upper and lower layers on the separation layer, so the thickness of the device is very limited, the invention can release the stress at the interface without generating polarization charges, meanwhile, a thicker multiplication layer can be grown on the separation layer, the electronic characteristic of the two-dimensional material depends on the number of layers to a great extent, and the band gap can be adjusted, thereby being beneficial to better matching the energy band of the two-dimensional material with the energy bands of other layers and facilitating the transmission of electrons.
(3) The avalanche photodetector adopts GeS two-dimensional material with 3680cm2V-1s-1Has a high electron mobility of 370cm higher than that of AlGaN2V-1s-1The conductivity of the device is higher, and the response speed is higher.
(4) The number of the n-type GeS separation layers of the avalanche photodetector is two, so that the problem that the band gap matching requirement is not met due to the fact that a single layer of GeS material is not stable enough and the band gap is reduced by multiple layers of GeS materials is solved.
(5) The method utilizes Van der Waals force to bond and grow the two-dimensional material GeS and the three-dimensional material AlGaN, has a steep interface, and avoids the problem of dopant diffusion of the isolation layer.
(6) According to the preparation method of the module I and the module II, the MOCVD method is adopted to grow from the lowest layer, and the device is not easy to grow thick.
Drawings
In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which
Fig. 1 is a schematic structural diagram of a solar blind ultraviolet avalanche photodetector of the present invention.
Fig. 2 is a graph of the current-voltage characteristics of the solar-blind ultraviolet avalanche photodetector of the present invention.
The reference numbers in the drawings are as follows:
AlN template layer 1, AlN buffer layer 2, n-type Alx1Ga1-x1N layer 3, N-type ohmic electrode 31, i-type Alx2Ga1-x2 N absorption layer 4, N-type GeS separation layer 5, i-type Alx3Ga1-x3N layer 6, p-type GaN layer 7, p-type ohmic electrode 71.
Detailed Description
(example 1)
The problem with the growth of the SAM-type avalanche photodetector process is solved by integrating and holding together two-dimensional materials and three-dimensional materials in the required stacking sequence by weak van der waals forces, because there are no dangling bonds at the interface of van der waals bonding, the interface is very clear and defect-free, and no perfect lattice matching is required. Considering the problem of band gap matching, we will adopt EgInstead of the AlGaN three-dimensional material of the separation layer n1, a GeS two-dimensional material of 3.4eV is used. If a two-dimensional material with a finer band gap is used, for example SeGe (E)g2.2eV), instead, it results in the formation of deeper potential hydrazine at the separation layer n1, so that more electrons will be retained in the potential hydrazine, which affects the performance of the whole device. Compared with the traditional three-dimensional material, the sheet of the layered material has multiple advantages in photoelectric detection, and most obviously, the material has adjustable band gap, so that the energy band of the material can be better matched with the energy bands of other layers, and the transmission of electrons is facilitated. Meanwhile, the selection of two-dimensional materials and the stability are also important, and the GeS single-layer phonon dispersion spectrum has no soft phonon mode and is a stable two-dimensional structure. The negative affinity potential of the GeS monolayer was 4.62 eV/atom, also indicating that the GeS monolayer has a strong bonding network.
The most important thing in integrating AlGaN three-dimensional material and GeS two-dimensional material is to reduce the activity and impurities on the surface of the three-dimensional material, and the surface activity is from the surfaceActive dangling bond of (1). AlGaN is an inorganic semiconductor material which is connected with atoms by covalent bonds, and the bond length and the angle of the covalent bonds are fixed, so that a large number of dangling bonds are arranged on the surface of the material. The van der waals bonding technology is used, a layered material without dangling bonds is used as a substrate, and when other materials are deposited on the substrate in a layered mode, the two materials are bonded by van der waals force. Although the binding energy of van der waals force is weak compared to the binding energy of covalent bond, the preparation of a grown material with its own lattice constant can be successfully accomplished even with a lattice mismatch as high as 50% in van der waals bonding technique compared to covalent bonding. Therefore, the treatment of dangling bonds and impurity contamination on the surface of the three-dimensional material is necessary and can be performed by an ex-situ treatment method. The ex-situ treatment mainly comprises wet etching the GaN substrate with HF, HCL, KOH solution, or UV/O3And treating the surface of the material to remove surface impurities. At the same time, there is evidence that the use of HF solutions is more effective for electrical and chemical passivation of semiconductor surfaces by "bridging" the bare dangling bonds with hydrogen atoms.
The detection waveband of the solar-blind ultraviolet avalanche detector is a solar-blind ultraviolet waveband, and light in the waveband is minimally interfered in the atmosphere, so that the light in the solar-blind ultraviolet waveband is most easily detected.
Referring to fig. 1, the solar-blind ultraviolet avalanche photodetector of this embodiment has a structure comprising, from bottom to top, an AlN template layer 1, an AlN buffer layer 2, and n-type Al in sequencex1Ga1-x1N layer 3, i type Alx2Ga1-x2 N absorption layer 4, N-type GeS separation layer 5, i-type Alx3Ga1-x3An N-multiplication layer 6 and a p-type GaN layer 7. The AlN template layer 1 employs a sapphire template substrate.
n type Alx1Ga1-x1An N-type ohmic electrode 31 is led out of the N layer 3, and a Ti/Al/Ni/Au alloy electrode is adopted; a p-type ohmic electrode 71 is led out of the p-type GaN layer 7, and a Ni/Au alloy electrode is adopted.
The n-type GeS separation layer 5 is respectively connected with the i-type Alx2Ga1-x2 N absorption layer 4 and i type Alx3Ga1-x3The N-fold increasing layer 6 is bonded by van der waals force to form a stable structure. The GeS layer of the n-type GeS separation layer 5 is arranged into two layers, wherein each layer is thickThe degree is 0.6nm, because the single-layer GeS material is not stable enough, the multi-layer GeS material can reduce the band gap and can not meet the requirement of band gap matching.
The thickness of the AlN template layer 1 is 500 nm; the AlN buffer layer 2 is 100-300 nm thick; n type Alx1Ga1-x1The thickness of the N layer 3 is 100-300 nm, wherein the Al component x1 is 0.6; type i Alx2Ga1-x2The thickness of the N absorption layer 4 is 150-220 nm, wherein the Al component x2 is 0.6; the thickness of the n-type GeS separation layer 5 is 1.2-1.8 nm; type i Alx3Ga1-x3The thickness of the N-times layer 6 is 150-200 nm, wherein the Al component x3 is 0.4; the thickness of the p-type GaN layer 7 is 10-300 nm.
The preparation method of the solar-blind ultraviolet avalanche photodetector of the embodiment comprises the following steps:
s1: manufacturing a first module, wherein the first module sequentially comprises an AlN template layer 1, an AlN buffer layer 2 and n-type Al from bottom to topx1Ga1-x1N layer 3 and i type Alx2Ga1-x2The specific method of the N absorption layer 4 is as follows:
s11: cleaning the sapphire template substrate as a module-substrate in NH3Nitriding the surface of the atmosphere for 3 minutes, and forming an AlN template layer 1 on a first substrate of the module;
s12: growing an AlN buffer layer 2 with the thickness of 200nm on the AlN template layer 1 of the module I by using an MOCVD method;
s13: growing a layer of n-type Al with the thickness of 200nm on the AlN buffer layer 2 of the module I by using an MOCVD method0.6Ga0.4N layer 3 with a doping concentration of 2X 1018cm-3；
S14: in n-type Al0.6Ga0.4Growing a layer of i-type Al with the thickness of 250nm on the N layer 3 by using an MOCVD method0.6Ga0.4 N absorption layer 4 with doping concentration of 2 × 1016cm-3；
S2: manufacturing a second module, wherein the second module sequentially comprises an AlN template layer 1, an AlN buffer layer 2, an i-type Alx3Ga1-x3N layer 6 and a p-type GaN layer 7 from bottom to top, and the specific method comprises the following steps:
s21: cleaning the sapphire template substrate as the second substrate of the module in NH3Nitriding the surface of the atmosphere for 3 minutes to form A on the two substrates of the modulelN template layer 1;
s22: respectively growing an AlN buffer layer 2 with the thickness of 200nm on the AlN template layer 1 of the module II by using an MOCVD method;
s23: growing a layer of i-type Al with the thickness of 150nm on the AlN buffer layer 2 of the second module by using an MOCVD method0.4Ga0.6N layer 6 with a doping concentration of 2 x 1016cm-3；
S24: in type i Al0.4Ga0.6A 185nm thick p-type GaN layer 7 with a doping concentration of 1 × 10 is grown on the N-times layer 6 by MOCVD method18cm-3；
S3: manufacturing a third module, wherein the third module comprises a third module substrate and an n-type GeS separation layer 5; manufacturing GeS with two layers of thickness, firstly synthesizing a GeS bulk thin sheet by using a chemical vapor deposition method, and then mechanically stripping the bulk thin sheet to a module three-substrate by using a transparent adhesive tape, wherein the module three-substrate is a Ni film, and the preparation steps of the GeSS separation layer 5 are as follows:
s31: placing a quartz boat filled with 10mg of GeS powder in the center of a quartz tube of a tube furnace;
s32: ultrasonically cleaning a Si substrate with the thickness of 500 mu m and the width of 3-5 mm in acetone and isopropanol respectively for 5 minutes, and drying by using high-purity nitrogen;
s33: placing a Si substrate at a position 12-15cm below the center of the tube furnace;
s34: evacuating the quartz tube to a basic pressure of 80-100 mTorr, flushing with high-purity Ar gas for 3 times, and introducing Ar gas at a rate of 10-30 sccm until the pressure is kept at 20-40 Torr;
s35: after the pressure is stable, heating the tube furnace to 400-500 ℃ at the speed of 50-60 ℃/min, and depositing for 1-10 min when the deposition temperature of the substrate reaches 290-330 ℃;
s36: after the deposition is finished, naturally cooling the tube furnace to room temperature to prepare GeS nano sheets;
s37: mixing 10g of GeS nano sheets with 1000g of purified water, stirring by using a stirrer at the rotating speed of 2000r/min for 20min, and finishing to obtain a GeS mixed solution;
s38: and adding 50.5g of surfactant NMP into the GeS mixed solution obtained by preliminary stirring and mixing, wherein the mass ratio of the surfactant NMP to the GeS mixed solution is 5: 100, continuously shearing and stripping for 4 hours by adopting a high-speed stripping machine, wherein the rotating speed of the stripping machine is 3500 +/-100 r/min, and obtaining a GeS solution;
s39: centrifuging the GeS solution obtained by shearing and stripping, placing the GeS solution into a centrifugal tube, sealing, placing the centrifugal tube into a groove in a centrifugal head, adjusting the centrifugal machine to rotate for 4000r/min, continuously centrifuging for 5min, taking out the centrifugal tube, removing upper water, and pouring the GeS liquid in the centrifugal tube into a culture dish;
s310: putting the culture dish filled with the centrifuged GeS liquid into a vacuum drying phase for drying, adjusting the temperature of a drying oven to 50 ℃ and the vacuum degree to 133Pa, and continuously drying for 24 hours to obtain a GeS product;
s311: GeS with the thickness of 4nm is grown on the sapphire wafer by using an MOCVD method;
s312: depositing a Ni film with the thickness of 600nm on GeS, and sticking a heat-insulating tape on the Ni film to be used as a treating agent;
s313: tearing the tape/Ni stack, separating the weakest GeS-sapphire interface, resulting in the release of the entire GeS film from the substrate;
s314: depositing a layer of Ni film at the bottom of the GeS film, applying a torque on the top Ni film to start the spalling mode fracture, guiding downward cracks, and repeatedly stripping;
s315: the Ni/GeS layer is separated after being peeled off, and the bottom Ni film has strong adhesive force with the GeS monolayer, so that the GeS monolayer is left on the bottom Ni film;
s4: stripping the AlN template layer 1 and the AlN buffer layer 2 of the second module by using a mechanical stripping method to prepare a combination of an i-type Alx3Ga1-x3N layer 6 and a p-type GaN layer 7;
s5: in i-type Al treated by ex-situ method0.6Ga0.4An N-type GeS separation layer 5 is combined on the N absorption layer 4 by using Van der Waals bonding technology; treatment of type i Al using ex situ methodsx2Ga1-x2 N absorption layer 4 and i type Alx3Ga1-x3The steps of the surface of the material of the N-times multiplication layer 6 are as follows:
s51: immersing the sample in an HF acid solution for 3 minutes;
S52：taking out N immediately2Drying, and putting into a vacuum system as soon as possible with a base pressure of not more than 5 × 10-9Torr, minimizing exposure to room air;
s53: under the condition of extra-high voltage, the base pressure is less than 5 multiplied by 10-9Torr, the thermal desorption process was carried out by heating the sample with a hot wire, the heating process was brought to the desired temperature at a rate of 75 deg.C/min and held for 15min before cooling.
S6: combining i-type Al treated by ex-situ method on n-type GeS separation layer 5 using van der Waals bonding technique0.4Ga0.6 An N-fold layer 6;
s7: etching a part of the p-type GaN layer 7 from the upper surface to n-type Al0.6Ga0.4 The N layer 3 forms a table top, and the surface of the etched sample is subjected to purification treatment;
s8: in n-type Al0.6Ga0.4Evaporating N-type ohmic electrode 31 on the N layer 3 mesa for 10min, evaporating at 800 deg.C2Annealing for 3 minutes under the environment;
s9: a p-type ohmic electrode 71 was deposited on the p-type GaN layer 7 for 10 minutes, and N was deposited at 800 ℃ after deposition2Annealing for 1 minute at ambient.
The method includes the steps that simulation is conducted on photoelectric characteristics of the solar blind ultraviolet avalanche photodetector of the embodiment by using Sentaurus TCAD simulation software, firstly codes are written in an sde module in the software to construct a structure of a device, and then physical models required by simulation, such as a carrier drift diffusion model, a generated composite current model, an interband tunneling model, an ionization multiplication model and the like, are added into the codes in an sdevice module. Because the polarization effect at the heterogeneous interface needs to be inhibited to reduce the avalanche breakdown voltage of the APD, after the special isolation layer is integrated, the stress is released at the interface, polarization charges cannot be generated, the polarization electric field can be reduced to a certain extent, so that the avalanche multiplication current is reduced, the breakdown voltage is increased, and the device is protected from breakdown; and the interface is steep without defect state, and simultaneously, the problem of dopant diffusion is solved, so that the influence of surface recombination current and drift diffusion current on the device is reduced. Fig. 2 is a graph showing a comparison between a dark current-voltage characteristic curve of the solar-blind ultraviolet avalanche photodetector integrated with a special isolation layer according to the present invention obtained by simulation and a current-voltage characteristic of a solar-blind ultraviolet avalanche photodetector integrated with a common isolation layer. As seen from FIG. 2, the current of the novel solar-blind ultraviolet avalanche photodetector integrated with a special isolation layer and the current of the common ultraviolet avalanche photodetector increase along with the increase of the voltage, and the composite current and the tunneling current are basically unchanged. After the critical electric field of the avalanche is reached, carriers continuously impact the crystal lattice, the number of the carriers in the avalanche region is sharply increased and moves to the vicinity of the electrode at a high speed to form dark current taking an avalanche multiplication mechanism as a main factor. In the figure, when the voltage is more than 40V, under the same voltage, the dark current of the novel solar blind ultraviolet avalanche photodetector integrated with the special isolation layer is obviously smaller than that of a common ultraviolet avalanche photodetector, and the avalanche breakdown voltage of the device is also larger than that of the common ultraviolet avalanche photodetector, so that the device cannot be broken down in advance.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A solar blind ultraviolet avalanche photodetector is characterized in that: the structure of the composite material sequentially comprises an AlN template layer (1), an AlN buffer layer (2) and n-type Al from bottom to topx1Ga1-x1N layer (3), i type Alx2Ga1-x2An N absorption layer (4), an N-type GeS separation layer (5), and an i-type Alx3Ga1-x3An N-multiplication layer (6) and a p-type GaN layer (7); the n-type Alx1Ga1-x1An N-type ohmic electrode (31) is led out from the N layer (3); a p-type ohmic electrode (71) is led out from the p-type GaN layer (7); the n-type GeS separation layer (5) is respectively connected with the i-type Alx2Ga1-x2N absorption layer (4) and i-type Alx3Ga1-x3The N-fold layer (6) is formed by combining Van der Waals bonding.
2. According to the claimsThe solar blind ultraviolet avalanche photodetector described in claim 1 is characterized in that: the AlN template layer (1) is 500nm thick; the AlN buffer layer (2) is 100-300 nm thick; the n-type Alx1Ga1-x1The thickness of the N layer (3) is 100-300 nm; the i-type Alx2Ga1-x2The thickness of the N absorption layer (4) is 150-220 nm; the thickness of the n-type GeS separation layer (5) is 1.2-1.8 nm; the i-type Alx3Ga1-x3The thickness of the N-time multiplication layer (6) is 150-200 nm; the thickness of the p-type GaN layer (7) is 10-300 nm.
3. The solar-blind ultraviolet avalanche photodetector of claim 1, wherein: the number of layers of the n-type GeS separation layer (5) is two.
4. The solar-blind ultraviolet avalanche photodetector of claim 3, wherein: the thickness of each n-type GeS separation layer (5) is the same.
5. The solar-blind ultraviolet avalanche photodetector of claim 1, wherein: the AlN template layer (1) adopts a sapphire template substrate.
6. A method of manufacturing a solar-blind ultraviolet avalanche photodetector as claimed in any one of claims 1 to 5, characterized by comprising the steps of:
s1: manufacturing a first module, wherein the first module sequentially comprises an AlN template layer (1), an AlN buffer layer (2) and n-type Al from bottom to topx1Ga1-x1N layer (3) and i type Alx2Ga1-x2An N absorption layer (4);
s2: manufacturing a second module, wherein the second module sequentially comprises an AlN template layer (1), an AlN buffer layer (2) and i-type Al from bottom to topx3Ga1-x3An N layer (6) and a p-type GaN layer (7);
s3: manufacturing a third module, wherein the third module comprises a third module substrate and an n-type GeS separation layer (5);
s4: stripping off the AlN template layer (1) and the AlN buffer layer (2) of the second module to obtain i-type Alx3Ga1-x3A combination of an N layer (6) and a p-type GaN layer (7);
s5: combining all layers from bottom to top to obtain the I-type Al of the module Ix2Ga1-x2I-type Al of N absorption layer (4) and module IIx3Ga1-x3The N multiplication layers (6) are processed by an ex-situ method, the N-type GeS separation layer (5) of the third module is peeled off from the third module substrate, and Van der Waals force bonding technology is respectively adopted to be bonded with the i-type Al of the first modulex2Ga1-x2I-type Al of N absorption layer (4) and module IIx3Ga1-x3Combining the N multiplication layers (6);
s6: etching a part of the p-type GaN layer (7) from the upper surface to n-type Alx1Ga1-x1The upper surface of the N layer (3) forms a table top, and the surface of the etched sample is subjected to purification treatment;
s7: in n-type Alx1Ga1-x1Evaporating an N-type ohmic electrode (31) on the table top of the N layer (3), and annealing the N-type ohmic electrode (31) after evaporation;
s8: a p-type ohmic electrode (71) is deposited on the p-type GaN layer (7), and the p-type ohmic electrode (71) is annealed after deposition.
7. The method for preparing a solar-blind ultraviolet avalanche photodetector as claimed in claim 6, wherein: the manufacturing method of the module I comprises the following steps:
s11: cleaning the sapphire substrate as a module-substrate in NH3Nitriding the first substrate of the module under the atmosphere, and forming an AlN template layer (1) on the first substrate of the module;
s12: growing an n-type AlN buffer layer (2) on the AlN template layer (1) of the module I;
s13: growing a layer of n-type Al on the AlN buffer layer (2) of the module Ix1Ga1-x1An N layer (3);
s14: in n-type Alx1Ga1-x1A layer of i-type Al grows on the N layer (3)x2Ga1-x2An N absorption layer (4).
8. The method for preparing a solar-blind ultraviolet avalanche photodetector as claimed in claim 6, wherein: the manufacturing method of the second module comprises the following steps:
s21: cleaning the sapphire substrate as the second substrate of the module at NH3Nitriding the second substrate of the module under the atmosphere, and forming an AlN template layer (1) on the second substrate of the module;
s22: growing an n-type AlN buffer layer (2) on the AlN template layer (1) of the second module;
s23: growing a layer of i-type Al on the AlN buffer layer (2) of the second modulex3 Ga1-x3 An N layer (6);
s24: in type i Alx3Ga1-x3And a p-type GaN layer (7) grows on the N multiplication layer (6).
9. The method for preparing a solar-blind ultraviolet avalanche photodetector as claimed in claim 6, wherein: and the preparation method of the module III adopts a chemical vapor deposition method to synthesize a GeS bulk thin sheet and mechanically peels the GeS bulk thin sheet onto a substrate of the module III.
10. The method for preparing a solar-blind ultraviolet avalanche photodetector as claimed in claim 6, wherein: the ex-situ treatment in the S5 comprises the following steps:
s51: immersing the sample in an HF acid solution for soaking;
s52: taking out N immediately2Drying and placing in a vacuum system with a base pressure of not more than 5 × 10-9Torr；
S53: under the condition of extra-high voltage, the base pressure is less than 5 multiplied by 10-9Torr, the sample was heated using a hot wire for a thermal desorption process and held for 15min before cooling.
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