A windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector and a preparation method thereof

Abstract

The application discloses a windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector and a preparation method thereof, and relates to an ultraviolet photodetector. The detector is provided with, from bottom to top, a silicon carbide high-doped n+ type substrate, a silicon carbide n type buffer layer, a silicon carbide low-doped n layer, a small-area uniformly distributed separated silicon carbide n type charge layer in the n layer, a silicon carbide low-doped n type multiplication layer on the n type charge layer, a windowed silicon carbide high-doped p+ type ohmic contact layer arranged at a position corresponding to the separated n type charge layer on the n type multiplication layer, a silicon dioxide passivation isolation layer arranged at a windowed position of the p+ type ohmic contact layer, a p+ type ohmic contact electrode arranged on a surface of the p+ type ohmic contact layer, and an n+ type ohmic contact electrode arranged on a back surface of the n+ type substrate. The multiple small-area SACM structures and i-n structures are combined, electric fields are connected and coupled with each other, photo-generated carriers are accelerated to the multiplication layer to generate avalanche breakdown, and weak ultraviolet signal detection is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to ultraviolet photodetector, especially to a windowed charge layer separation SACM structure silicon carbide ultraviolet avalanche photodetector and a preparation method thereof. BACKGROUND

[0002] Ultraviolet (UV) photodetector has extremely high military and civil value, and is mainly applied to deep space exploration, environmental detection, ultraviolet sterilization and national defense field. At present, high response photomultiplier tube (PMT) is widely used in photodetectors for detecting weak ultraviolet signals, but it has many shortcomings, such as large size, easy to damage, need high-precision high-voltage power supply, high cost and cannot effectively realize array detection, etc., so developing semiconductor ultraviolet photodetector to replace photomultiplier tube has become a research hotspot in the field of photodetection in recent years.

[0003] At present, the mainstream semiconductor detection technology of ultraviolet band signal mainly adopts silicon-based detector, but due to its narrow band gap of only 1.12 eV, an expensive high-pass optical filter needs to be added in the test process to isolate the visible and infrared band light auxiliary test, thereby causing the effective light-sensitive area of the device system itself to be greatly reduced. In addition, the silicon ultraviolet photodetector also has some disadvantages, such as low quantum efficiency in the ultraviolet region, low detection rate, weak radiation resistance, etc. The wide band gap semiconductor photodetector can accurately detect the ultraviolet signal. Silicon carbide, as the main material of the third generation of wide band gap semiconductor, has excellent characteristics such as wide band gap, high breakdown electric field, high carrier saturation rate and high thermal conductivity. Therefore, the silicon carbide-based ultraviolet photodetector has high quantum efficiency, visible blindness, radiation resistance, high temperature resistance and other excellent properties. The silicon carbide-based ultraviolet photodetector generally has four types of Schottky, metal-semiconductor-metal (MSM), p-i-n and avalanche photodiode (APD). The APD includes p-i-n, absorption layer and multiplication layer separation (SAM), absorption layer, charge layer and multiplication layer separation (SACM) structures, and generally has the advantages of high gain, high responsivity, high quantum efficiency, and can detect weak ultraviolet light signals. In the traditional SACM structure APD, due to the high doping concentration of the charge layer, the drift of the photo-generated carriers will play a certain blocking role, which will cause the detector to be easily broken down, and it is difficult to realize high spectral responsivity and external quantum efficiency of the avalanche multiplication photodetector (Wu J, Zhang M, Fu Z, et al. Charge layer optimized 4H-SiC SACM avalanche photodiode with low breakdown voltage and high gain[J]. Japanese Journal of Applied Physics, 2019, 58(10):100913-). Therefore, how to optimize the device structure of the traditional SACM structure APD to improve the spectral responsivity and quantum efficiency of the detector has become a new direction of research on silicon carbide ultraviolet avalanche photodetectors. SUMMARY

[0004] The purpose of the present application is to provide a windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector and a preparation method thereof. The spectral responsivity and external quantum efficiency of the detector can be effectively improved compared with the traditional silicon carbide SACM ultraviolet avalanche photodetector, and the dark current and avalanche voltage of the detector are reduced compared with the traditional silicon carbide SACM ultraviolet avalanche photodetector.

[0005] To achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0006] The application discloses a windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector, which is characterized in that: a silicon carbide high-doped n+ type substrate is used as a base; a silicon carbide n type buffer layer is arranged on the n+ type substrate; a silicon carbide low-doped n- layer is arranged upwards at a central position of the n type buffer layer; small-area and uniformly distributed separated n type charge layers are arranged in the n- layer; a silicon carbide low-doped n- type absorption layer is arranged below the n type charge layer, and is used for absorbing ultraviolet light and generating photo-generated carriers; a silicon carbide low-doped n- type multiplication layer is arranged above the n type charge layer, and is used for realizing a multiplication effect of the carriers under a high electric field; a windowed silicon carbide high-doped p+ type ohmic contact layer is arranged at a position corresponding to the separated n type charge layer on the n- type multiplication layer, and is used for allowing the ultraviolet light to directly incident on the n- type absorption layer and reducing a recombination problem of the photo-generated carriers; a silicon dioxide passivation isolation layer is arranged at a window of the p+ type ohmic contact layer, and is used for protecting the device; a p+ type ohmic contact electrode is arranged on an upper surface of the p+ type ohmic contact layer, and is used for electrical connection; and an n+ type ohmic contact electrode is arranged on a back surface of the n+ type substrate.

[0007] The whole device is composed of a plurality of small-area absorption layers, charge layers and multiplication layers of a separated (SACM) structure and a plurality of small-area i-n structures, electric fields of adjacent SACM structures are connected and coupled with each other, photo-generated carriers generated in the i-n structure can be accelerated and drifted to the n- type multiplication layer of the SACM structure by the coupled electric field, under the acceleration effect of the high electric field, the carriers in the n- type multiplication layer and atomic valence bonds in the crystal lattice interact with each other, collision ionization is generated, avalanche breakdown is realized, multiplication detection of the weak ultraviolet signal is realized, the weak ultraviolet signal is effectively multiplied, the avalanche voltage and the dark current of the device are reduced under the premise of ensuring the uniformity of the avalanche, meanwhile, the ultraviolet light can directly incident on the n- type absorption layer at the window of the p+ type ohmic contact layer, the recombination problem of the photo-generated carriers is reduced, and the spectral responsivity, the external quantum efficiency and the detectivity of the device are effectively improved.

[0008] The longitudinal section width of the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector can be 100-200 microns; the n+ type substrate can adopt a commercial n+ conductive substrate, the width of the substrate can be 100-200 microns, the thickness can be 50-800 microns, and the doping concentration order of magnitude can be 10 19 / cm 3 -10 20 / cm 3 ; the width of the n type buffer layer can be 100-200 microns, the thickness can be 100 nanometers-1 micron, and the doping concentration order of magnitude can be 10 18 / cm 3 -10 19 / cm 3; the n-type absorption layer can have a width of 100-200 μm, a thickness of 1-3 μm, and a doping concentration of 10 15 / cm 3 ~10 16 / cm 3 ; each n-type charge layer can have a width of 5-10 μm, a thickness of 100-200 nm, and a doping concentration of 10 17 / cm 3 ~10 18 / cm 3 ; the adjacent n-type charge layers can be spaced apart by a width of 5-10 μm and a thickness of 100-200 nm; the n-type multiplication layer can have a width of 100-200 μm, a thickness of 300-700 nm, and a doping concentration of 10 15 / cm 3 ~10 16 / cm 3 ; each p+ type ohmic contact layer can have a width of 5-10 μm, a thickness of 200-300 nm, and a doping concentration of 10 19 / cm 3 ~10 20 / cm 3 ; the adjacent p+ type ohmic contact layers can be spaced apart by a width of 5-10 μm and a thickness of 200-300 nm; each p+ type ohmic contact layer can be provided with a silicon dioxide passivation isolation layer at the window, and the passivation isolation layer can also be a wide-bandgap passivation isolation material such as hafnium oxide, and can have a thickness of 10 nm-2 μm.

[0009] The application also provides a preparation method of the windowed charge layer separated SACM structure carbonized silicon ultraviolet avalanche photodetector.

[0010] 1) RCA standard cleaning of a high-doped n+ type carbonized silicon substrate;

[0011] 2) epitaxial growth of a carbonized silicon n-type buffer layer on the high-doped n+ type carbonized silicon substrate;

[0012] 3) epitaxial growth of a low-doped n-type carbonized silicon layer on the carbonized silicon n-type buffer layer;

[0013] 4) formation of a plurality of uniformly distributed small-area n-type charge layers in the n-type layer by using deposition, photolithography, etching, ion implantation, and high-temperature annealing technology, wherein the n-type charge layer is below a low-doped n-type absorption layer and above a low-doped n-type multiplication layer;

[0014] 5) epitaxial growth of a high-doped p+ type ohmic contact layer on the low-doped n-type multiplication layer;

[0015] 6) Using deposition, lithography and etching technology in p+ type ohmic contact layer corresponding to the interval of the n-type charge layer etching out the window of uniform distribution;

[0016] 7) Using thermal oxidation and PECVD technology in p+ type ohmic contact layer window to form a wide band gap passivation layer of silicon dioxide or hafnium oxide;

[0017] 8) Using lithography, magnetron sputtering and annealing technology in the surface of high-doped p+ type ohmic contact layer and n+ type substrate bottom to prepare p+ type ohmic contact electrode and n+ type ohmic contact electrode respectively.

[0018] The conventional SACM structure silicon carbide ultraviolet avalanche photodetector of the prior art is prone to breakdown in advance if the doping concentration of the charge layer is high, which results in that it is difficult to realize high spectral responsivity and quantum efficiency of avalanche multiplication photodetection; if the doping concentration of the charge layer is low, the modulation effect on the avalanche electric field is reduced, which results in that the avalanche voltage of the detector is too high and cannot meet the industrial demand of APD.

[0019] Compared with the prior art, the present application has the following outstanding advantages: the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector designed in the present application is composed of a plurality of small-area absorption layers, charge layers and multiplication layers separated (SACM) structure and a plurality of small-area i-n structures, the electric fields of adjacent SACM structures are connected and coupled with each other, the photo-generated carriers generated in the i-n structure can be accelerated and drifted by the coupled electric field to the n-type multiplication layer of the SACM structure, under the acceleration effect of the high electric field, the carriers in the n-type multiplication layer and the atomic valence bond in the crystal lattice interact with each other to produce collision ionization, thereby producing avalanche breakdown, realizing multiplication detection of weak ultraviolet signals, reducing the avalanche area under the premise of ensuring the uniformity of the avalanche, and effectively reducing the dark current of the device; at the same time, the ultraviolet light can directly enter the n-type absorption layer at the window of the p+ type ohmic contact layer, reducing the recombination problem of the photo-generated carriers, effectively improving the spectral responsivity, external quantum efficiency and detection rate of the device, the high built-in electric field is easily generated at the edge of the window of the p+ type ohmic contact layer, which promotes the built-in electric field in the n-type multiplication layer to quickly reach the silicon carbide avalanche critical electric field, effectively reducing the avalanche voltage of the device. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The cross-sectional schematic view of the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector described in the embodiments of the present application.

[0021] Figure 2 The dark current comparison chart of the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector described in the embodiments of the present application and the traditional SACM structure ultraviolet avalanche photodetector.

[0022] Figure 3 The spectral responsivity curves of the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector and the conventional SACM structure ultraviolet avalanche photodetector under a reverse bias of 20V are compared.

[0023] In Figure 1 , each mark is:

[0024] (1) silicon carbide high-doped n+ substrate, (2) silicon carbide n-type buffer layer, (3) silicon carbide low-doped n-type absorption layer, (4) separated silicon carbide n-type charge layer, (5) silicon carbide low-doped n-type multiplication layer, (6) windowed silicon carbide high-doped p+ ohmic contact layer, (7) silicon dioxide passivation isolation layer, (8) p+ ohmic contact electrode, (9) n+ ohmic contact electrode. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present application more clear, the following embodiments will be further described in combination with the drawings. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0026] In order to make the structure designed by the present application more clear and easy to understand, see Figure 1 The cross-sectional schematic diagram of the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector is shown in the embodiment of the present application.

[0027] The windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector is provided from bottom to top with:

[0028] The commercial silicon carbide high-doped n+ substrate (1) has a thickness of 50-800μm, and a doping concentration of 10 19 / cm 3 -10 20 / cm 3 , and a longitudinal cross-sectional width of 100-200μm; the silicon carbide n-type buffer layer (2) is arranged on the silicon carbide high-doped n+ substrate (1), and has a width of 100-200μm, a thickness of 100nm-1μm, and a doping concentration of 10 18 / cm 3 -10 19 / cm 3 ;

[0029] In the center of the carbon nitride n-type buffer layer (2) upwardly is provided a carbon nitride low-doped n-type absorption layer (3), the width of the carbon nitride low-doped n-type absorption layer (3) can be 100-200 μm, the thickness can be 1-3 μm, and the doping concentration order of magnitude can be 10 15 / cm 3 ~10 16 / cm 3 ; in the carbon nitride low-doped n-type absorption layer (3) is provided a small-area uniformly distributed separate carbon nitride n-type charge layer (4), the width of each separate carbon nitride n-type charge layer (4) can be 5-10 μm, the thickness can be 100-200 nm, and the doping concentration order of magnitude can be 10 17 / cm 3 ~10 18 / cm 3 , the width of the interval between adjacent separate carbon nitride n-type charge layers (4) can be 5-10 μm, and the thickness can be 100-200 nm; below the separate carbon nitride n-type charge layer (4) is the carbon nitride low-doped n-type absorption layer (3); above the n-type charge layer (4) is a carbon nitride low-doped n-type multiplication layer (5), the width of the carbon nitride low-doped n-type multiplication layer (5) can be 100-200 μm, the thickness can be 300-700 nm, and the doping concentration order of magnitude can be 10 15 / cm 3 ~10 16 / cm 3 ; on the carbon nitride low-doped n-type multiplication layer (5) is provided a windowed carbon nitride high-doped p+ type ohmic contact layer (6) corresponding to the separate carbon nitride n-type charge layer (4), the width of each windowed carbon nitride high-doped p+ type ohmic contact layer (6) can be 5-10 μm, the thickness can be 200-300 nm, and the doping concentration order of magnitude can be 10 19 / cm 3 ~10 20 / cm 3 , the width of the etching window of adjacent windowed carbon nitride high-doped p+ type ohmic contact layers (6) can be 5-10 μm, and the thickness can be 200-300 nm; on the windowed carbon nitride high-doped p+ type ohmic contact layer (6) is provided a silicon dioxide passivation isolation layer (7), the dielectric layer material of the silicon dioxide passivation isolation layer (7) can be silicon dioxide, hafnium oxide or silicon nitride, etc., and the thickness of the silicon dioxide passivation isolation layer (7) can be 10 nm-2 μm; on the upper surface of the windowed carbon nitride high-doped p+ type ohmic contact layer (6) is provided a p+ type ohmic contact electrode (8), and on the back surface of the carbon nitride high-doped n+ type substrate (1) is provided an n+ type ohmic contact electrode (9).

[0030] The whole device is composed of a plurality of small-area absorption layers, charge layers and multiplication layers separated (SACM) structure and a plurality of small-area i-n structure, the electric field of adjacent SACM structure is connected and coupled, the photo-generated carriers generated in the i-n structure can be accelerated and drifted to the n-type multiplication layer of the SACM structure by the coupled electric field, under the acceleration of high electric field, the carriers in the n-type multiplication layer and the atomic valence bond in the crystal lattice interact with each other to produce collision ionization, thereby producing avalanche breakdown, realizing multiplication detection of weak ultraviolet signal, reducing the avalanche voltage and dark current of the device under the premise of ensuring the uniformity of the avalanche; at the same time, the ultraviolet light can directly enter the n-type absorption layer through the window of the p+ type ohmic contact layer, reducing the recombination of photo-generated carriers and effectively improving the spectral responsivity, external quantum efficiency and detectivity of the device.

[0031] The preparation method of the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector comprises the following steps:

[0032] 1) RCA standard cleaning is performed on a silicon carbide high-doped n+ type substrate;

[0033] 2) a silicon carbide n-type buffer layer is epitaxially grown on the silicon carbide high-doped n+ type substrate;

[0034] 3) a silicon carbide low-doped n-layer is epitaxially grown on the silicon carbide n-type buffer layer;

[0035] 4) a plurality of uniformly distributed small-area silicon carbide n-type charge layers are formed in the n-layer by using deposition, photolithography, etching, ion implantation and high-temperature annealing technology, the n-type charge layer is below a silicon carbide low-doped n-type absorption layer, and the n-type charge layer is above a silicon carbide low-doped n-type multiplication layer;

[0036] 5) a silicon carbide high-doped p+ type ohmic contact layer is epitaxially grown on the silicon carbide low-doped n-type multiplication layer;

[0037] 6) uniformly distributed windows are etched in the p+ type ohmic contact layer corresponding to the separated n-type charge layers by using deposition, photolithography and etching technology;

[0038] 7) a wide-bandgap passivation isolation layer such as silicon dioxide or hafnium oxide is formed at the window of the p+ type ohmic contact layer by using thermal oxidation and PECVD technology;

[0039] 8) a p+ type ohmic contact electrode and an n+ type ohmic contact electrode are respectively prepared on the surface of the high-doped p+ type ohmic contact layer and the bottom of the n+ type substrate by using photolithography, magnetron sputtering and annealing technology.

[0040] The following gives a specific preparation example.

[0041] 1) RCA standard cleaning is performed on a silicon carbide high-doped n+ type substrate (1) sample, and the steps are as follows:

[0042] a. Ultrasonic cleaning with toluene, acetone and ethanol at least twice, followed by rinsing with deionized water.

[0043] b. Use liquid No. 3 to cook at 250 ℃ for 20min, rinse with hot and cold deionized water, the liquid No. 3 is mixed in a ratio of H2SO4:H2O2=4:1 by volume.

[0044] c. Soak the sample in diluted hydrofluoric acid (hydrogen fluoride: deionized water = 1:10 by volume) for 3 minutes or more, then rinse with hot and cold deionized water.

[0045] d. Place the sample in solution No. 1 and boil for 10 minutes or more, then rinse with hot and cold deionized water. The solution No. 1 is a mixture of NH3·H2O:H2O2:H2O in a volume ratio of 1:1:4.

[0046] e. Place the sample in solution No. 2 and cook for 10 minutes or more, then rinse with hot and cold deionized water. The solution No. 1 is prepared in a volume ratio of HCl: H2O2: H2O = 1:1:4.

[0047] f. Soak the sample in diluted hydrofluoric acid (hydrogen fluoride: deionized water = 1:10 by volume) for 3 minutes or more, then rinse with hot and cold deionized water, blow dry the substrate with nitrogen, and set aside.

[0048] 2) The doping concentration of the (0001) Si surface epitaxial growth of the highly doped n+ type silicon carbide substrate (1) after RCA standard cleaning is on the order of 10 18 / cm 3 ~10 19 / cm 3 , a silicon carbide n-type buffer layer (2) having a width of 100 μm to 200 μm and a thickness of 100 nm to 1 μm;

[0049] 3) Epitaxial growth of doping concentration on SiC n-type buffer layer is on the order of 10 15 / cm 3 ~10 16 / cm 3 , a silicon carbide n-layer having a width of 100 μm to 200 μm and a thickness of 1 μm to 3 μm;

[0050] 4) Using photolithography, etching and deposition technology to form a mask, on this basis, phosphorus ions are implanted into the n-layer, and high temperature annealing is used to activate the phosphorus ions to form multiple evenly distributed small-area separated silicon carbide n-type charge layers (4) in the n-layer. The width of each separated silicon carbide n-type charge layer (4) can be 5μm to 10μm, the thickness can be 100nm to 200nm, and the doping concentration can be on the order of 10 17 / cm3 ~ 10 18 / cm 3 The width of the interval between adjacent separated silicon carbide n-type charge layers (4) can be 5-10 μm, and the thickness can be 100-200 nm. Below the n-type charge layer is a silicon carbide low-doped n-type absorption layer (3), and above the n-type charge layer is a silicon carbide low-doped n-type multiplication layer (5);

[0051] 5) A silicon carbide low-doped n-type multiplication layer (5) is epitaxially grown on the silicon carbide low-doped n-type absorption layer (3), and the doping concentration is 10 19 / cm 3 ~ 10 20 / cm 3 The width is 100-200 μm, and the thickness is 200-300 nm;

[0052] 6) A windowed silicon carbide high-doped p+ type ohmic contact layer (6) is etched in the silicon carbide low-doped n-type multiplication layer (5) corresponding to the interval between the separated silicon carbide n-type charge layers (4) by using deposition, lithography and etching technology. The width of each windowed silicon carbide high-doped p+ type ohmic contact layer (6) is 5-10 μm, the thickness is 200-300 nm, and the doping concentration is 10 19 / cm 3 ~ 10 20 / cm 3 The width of the etched window in the adjacent windowed silicon carbide high-doped p+ type ohmic contact layer (6) is 5-10 μm, and the thickness is 200-300 nm;

[0053] 7) The sample is cleaned according to the RCA standard to remove impurities on the surface of the sample. A layer of oxide is grown on the surface of the sample (n-type absorption layer upper surface direction) by using dry oxygen, wet oxygen and dry oxygen alternating oxidation as a sacrificial layer. The sample with the grown sacrificial layer is placed in a buffer hydrofluoric acid for etching to remove the sacrificial layer. A 10-60 nm thick thermal oxide silicon dioxide passivation isolation layer (7) is grown by using dry oxygen, wet oxygen, dry oxygen and nitrogen alternating oxidation. After the sacrificial layer is removed, a 10-2 μm wide band gap passivation material such as silicon dioxide or hafnium oxide can be grown by using PECVD technology as the silicon dioxide passivation isolation layer (7);

[0054] 8) using photoetching process, exposing and developing photoresist, using buffered hydrofluoric acid to etch the oxide layer on the upper part of the windowed silicon carbide high-doped p+ type ohmic contact layer to form an electrode window, using magnetron sputtering process to prepare an alloy layer to form a p+ type ohmic contact electrode (8), preparing a photoresist layer on the front surface of the sample for protection and isolation, using buffered hydrofluoric acid to etch the oxide layer on the bottom surface of the substrate, using magnetron sputtering to prepare an alloy layer to form an n+ type ohmic contact electrode (9), annealing the two electrodes, so that the windowed silicon carbide high-doped p+ type ohmic contact layer (8) and the n+ type ohmic contact electrode (9) of the sample form good ohmic contacts with the windowed silicon carbide high-doped p+ type ohmic contact layer (6) and the silicon carbide high-doped n+ type substrate (1) respectively.

[0055] Figure 2 The dark current comparison chart of the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector and the conventional SACM structure ultraviolet avalanche photodetector is shown in the embodiment of the present application. Figure 2 It can be seen that, compared with the conventional SACM ultraviolet avalanche photodetector, the dark current of the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector is reduced by 62.0%, and the avalanche voltage is reduced by 13.5%.

[0056] Figure 3 The spectral responsivity curve comparison chart of the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector and the conventional SACM structure ultraviolet avalanche photodetector under a reverse bias voltage of 20V is shown in the embodiment of the present application. Figure 3 It can be seen that, compared with the conventional SACM ultraviolet avalanche photodetector, the peak spectral responsivity of the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector is improved by 51.0%.

[0057] The above embodiments are only preferred embodiments of the present application and cannot be considered as limiting the scope of the present application. Any equivalent changes and improvements made according to the scope of the present application should still belong to the patent coverage of the present application.

Claims

1. A windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector, characterized in that The bottom-up silicon carbide high-doped n+ substrate is provided with a silicon carbide n-type buffer layer, a silicon carbide low-doped n-layer is provided at the center of the silicon carbide n-type buffer layer, a small-area uniformly distributed separate silicon carbide n-type charge layer is provided in the silicon carbide low-doped n-layer for avalanche field modulation and uniformity maintenance, a silicon carbide low-doped n-type absorption layer is provided under the separate silicon carbide n-type charge layer for light-generated carrier depletion, a silicon carbide low-doped n-type multiplication layer is provided above the separate silicon carbide n-type charge layer for light-generated carrier multiplication, a windowed silicon carbide high-doped p+ ohmic contact layer is provided on the silicon carbide low-doped n-type multiplication layer corresponding to the separate n-type charge layer for light-generated carrier collection, a silicon dioxide passivation isolation layer is provided on the windowed silicon carbide high-doped p+ ohmic contact layer, and a p+ ohmic contact electrode is provided on the surface of the windowed silicon carbide high-doped p+ ohmic contact layer, and an n+ ohmic contact electrode is provided on the back of the silicon carbide high-doped n+ substrate.

2. The windowed charge layer separated SACM structure SiC UV avalanche photodetector of claim 1, wherein The device is composed of a plurality of small-area absorption layers, charge layers and multiplication layers of separate SACM structure and a plurality of small-area i-n structures, the electric fields of adjacent SACM structures are connected and coupled with each other, the light-generated carriers generated in the i-n structure are accelerated and drifted to the n-type multiplication layer of the SACM structure by the coupled electric field, under the acceleration of the high electric field, the carriers in the n-type multiplication layer and the atomic valence bond in the crystal lattice interact with each other to produce collision ionization, thereby producing avalanche breakdown, achieving multiplication detection of weak ultraviolet signals, and reducing the avalanche voltage and dark current of the device under the premise of ensuring the uniformity of the avalanche; meanwhile, the ultraviolet light directly enters the n-type absorption layer at the window of the p+ ohmic contact layer, reducing the recombination of the light-generated carriers, and effectively improving the spectral responsivity, external quantum efficiency and detectivity of the device.

3. The windowed charge layer separated SACM structure SiC UV avalanche photodetector of claim 1, wherein The width of the silicon carbide high-doped n+ type substrate is 100-200 μm, the thickness is 50-800 μm, the doping concentration is 10 19 / cm 3 -10 20 / cm 3 .

4. The windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector according to claim 1, characterized in that The carbon nitride n-type buffer layer has a width of 100-200 μm, a thickness of 100 nm-1 μm, and a doping concentration of 10 18 / cm 3 -10 19 / cm 3 .

5. The windowed charge layer separated SACM structure SiC UV avalanche photodetector of claim 1, wherein The width of the low-doped n-type silicon carbide absorption layer is 100-200 μm, the thickness is 1-3 μm, and the doping concentration is 10 15 / cm 3 -10 16 / cm 3 .

6. The windowed charge layer separated SACM structure SiC UV avalanche photodetector of claim 1, wherein The width of each separated n-type carbonization charge layer is 5-10 μm, the thickness is 100-200 nm, and the doping concentration is 10 17 / cm 3 ~10 18 / cm 3 The width of the interval between adjacent separated n-type carbonization charge layers is 5-10 μm, and the thickness is 100-200 nm.

7. The windowed charge layer separated SACM structure SiC UV avalanche photodetector of claim 1, wherein The width of the silicon carbide low-doped n-type multiplication layer is 100-200 μm, the thickness is 300-700 nm, and the doping concentration is 10 15 / cm 3 ~ 10 16 / cm 3 .

8. The windowed charge layer separated SACM structure SiC UV avalanche photodetector of claim 1, wherein The width of each windowed silicon carbide high-doped p+ type ohmic contact layer is 5-10 μm, the thickness is 200-300 nm, and the doping concentration is 10 19 / cm 3 -10 20 / cm 3 . The width of the etching window in the adjacent windowed silicon carbide high-doped p+ type ohmic contact layer is 5-10 μm, and the thickness is 200-300 nm.

9. The windowed charge layer separated SACM structure SiC UV avalanche photodetector of claim 1, wherein The window of each windowed silicon carbide high-doped p+ ohmic contact layer is provided with a silicon dioxide passivation isolation layer, and the silicon dioxide passivation isolation layer can also be replaced with a wide-bandgap passivation isolation material such as hafnium oxide, and the thickness can be 10 nm to 2 μm.

10. The method of claim 1, wherein the method further comprises: forming a windowed charge layer separation SACM structure SiC UV avalanche photodetector. The method comprises the following steps: 1) RCA standard cleaning is performed on the silicon carbide high-doped n+ substrate; 2) a silicon carbide n-type buffer layer is epitaxially grown on the silicon carbide high-doped n+ substrate; 3) a silicon carbide low-doped n-layer is epitaxially grown on the silicon carbide n-type buffer layer; 4) a plurality of uniformly distributed small-area silicon carbide n-type charge layers are formed in the n-layer by deposition, photolithography, etching, ion implantation and high-temperature annealing technology, an n-type absorption layer is provided under the n-type charge layer, and an n-type multiplication layer is provided above the n-type charge layer; 5) a silicon carbide high-doped p+ ohmic contact layer is epitaxially grown on the silicon carbide low-doped n-type multiplication layer; 6) uniformly distributed windows are etched in the p+ ohmic contact layer corresponding to the interval of the separate n-type charge layer by deposition, photolithography and etching technology; 7) a wide-bandgap passivation isolation layer such as silicon dioxide or hafnium oxide is formed at the window of the p+ ohmic contact layer by thermal oxidation and PECVD technology. 8) The p+ type ohmic contact electrode and the n+ type ohmic contact electrode are prepared respectively on the surface of the high-doped p+ type ohmic contact layer and the bottom of the n+ type substrate by using photolithography, magnetron sputtering and annealing technology.

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