Windowing type charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector and preparation method thereof

Abstract

The invention discloses a windowing type 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 a silicon carbide highly-doped n + type substrate, a silicon carbide n-type buffer layer and a silicon carbide lowly-doped n-layer from bottom to top, separated silicon carbide n-type charge layers which are uniformly distributed in a small area are arranged in the n-layer, and a silicon carbide lowly-doped n-type multiplication layer is arranged on the n-type charge layers. A windowing type silicon carbide highly-doped p + type ohmic contact layer is arranged at the position, corresponding to the separated n type charge layer, of the n-type multiplication layer, a silicon dioxide passivation isolation layer is arranged at the windowing position of the p + type ohmic contact layer, a p + type ohmic contact electrode is arranged on the upper surface of the p + type ohmic contact layer, and an n + type ohmic contact electrode is arranged on the back face of the n + type substrate. The device is composed of a plurality of small-area SACM structures and i-n structures, electric fields are mutually connected and coupled, photon-generated carriers are accelerated to a multiplication layer to generate avalanche breakdown, and weak ultraviolet signal detection is achieved.

Description

Technical Field

[0001] The invention relates to an ultraviolet photoelectric detector, in particular to a window-type charge layer separated SACM structure silicon carbide ultraviolet avalanche photoelectric detector and a preparation method thereof. Background Art

[0002] Ultraviolet (UV) photodetectors have extremely high military and civilian value and are mainly used in deep space exploration, environmental monitoring, UV disinfection and national defense. Nowadays, high-responsivity photomultiplier tubes (PMTs) are widely used as photodetectors for detecting weak UV signals. However, they have many shortcomings, such as large size, easy damage, high-precision high-voltage power supply, high cost and inability to effectively realize array detection. Therefore, the development of semiconductor UV photodetectors to replace photomultiplier tubes has become a research hotspot in the field of photoelectric detection in recent years.

[0003] At present, the mainstream semiconductor detection technology for ultraviolet signals mainly adopts silicon-based detectors. However, due to its narrow bandgap of only 1.12 eV, it is necessary to add expensive high-pass optical filters during the test process to isolate the light-assisted test in the visible and infrared bands, which leads to a significant reduction in the effective photosensitive area of ​​the device system itself. At the same time, silicon ultraviolet photodetectors still have some disadvantages: for example, low quantum efficiency in the ultraviolet region, low detection rate, weak radiation resistance, etc., while wide-bandgap semiconductor photodetectors can accurately detect ultraviolet signals. Silicon carbide, as the main material of the third-generation wide-bandgap semiconductors, has excellent properties such as wide bandgap, high breakdown electric field, high carrier saturation rate, and high thermal conductivity. Therefore, silicon carbide-based ultraviolet photodetectors have excellent properties such as high quantum efficiency, visible blindness, radiation resistance, and high temperature resistance. Silicon carbide-based ultraviolet photodetectors generally include four types: Schottky, metal-semiconductor-metal (MSM), pin, and avalanche photodiode (APD). Among them, APD includes pin, absorption layer and multiplication layer separation (SAM), absorption layer, charge layer and multiplication layer separation (SACM) and other structures, which generally have the advantages of high gain, high responsiveness, high quantum efficiency, and the ability to detect weak ultraviolet light signals. In traditional SACM structure APD, due to the high doping concentration of the charge layer, the drift of photogenerated carriers will be blocked to a certain extent, which will cause the detector to break down early, making it difficult to achieve avalanche multiplication photodetection with high spectral responsivity and external quantum efficiency (Wu J, Zhang M, Fu Z, et al. Charge layer optimized 4H-SiC SACMavalanche 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 so that the spectral responsivity and quantum efficiency of the detector can be improved has become a new research direction for silicon carbide ultraviolet avalanche photodetectors. Summary of the invention

[0004] The purpose of the present invention 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 traditional silicon carbide SACM ultraviolet avalanche photodetectors. At the same time, the dark current and avalanche voltage of the detector are reduced compared with traditional silicon carbide SACM ultraviolet avalanche photodetectors.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A window-type charge layer separation SACM structure silicon carbide ultraviolet avalanche photodetector is provided with a silicon carbide highly doped n+ type substrate as a base; a silicon carbide n-type buffer layer is provided on the n+ type substrate; a silicon carbide low-doped n- layer is provided upward from the center of the n-type buffer layer; a small-area and uniformly distributed separated silicon carbide n-type charge layer is provided in the n- layer; a silicon carbide low-doped n-type absorption layer is provided below the n-type charge layer for absorbing ultraviolet light and generating photogenerated carriers; a silicon carbide low-doped n-type multiplication layer is provided above the n-type charge layer A layer is provided on the n-type multiplication layer, which is used to realize the multiplication effect of carriers under high electric field; a window-type silicon carbide highly doped p+ type ohmic contact layer is provided at the position corresponding to the separated n-type charge layer on the n-type multiplication layer, which is used to allow ultraviolet light to be directly incident on the n-type absorption layer and reduce the recombination problem of photogenerated carriers; a silicon dioxide passivation isolation layer is provided at the window of the p+ type ohmic contact layer to protect the device; a p+ type ohmic contact electrode is provided on the upper surface of the p+ type ohmic contact layer for electrical connection; and an n+ type ohmic contact electrode is provided on the back side of the n+ type substrate.

[0007] The entire device consists of multiple small-area absorption layers, charge layer and multiplication layer separation (SACM) structures and multiple small-area in structures. The electric fields of adjacent SACM structures are interconnected and coupled, so that the photogenerated carriers generated in the in structure can be accelerated by the coupled electric field and drifted to the n-type multiplication layer of the SACM structure. Under the acceleration of the high electric field, the carriers in the n-type multiplication layer interact with the atomic valence bonds in the lattice to produce collision ionization, thereby producing avalanche breakdown, realizing multiplied detection of weak ultraviolet signals, effectively multiplying the detection of weak ultraviolet signals, and reducing the avalanche voltage and dark current of the device while ensuring avalanche uniformity; at the same time, ultraviolet light at the window of the p+ type ohmic contact layer can be directly incident on the n-type absorption layer, reducing the recombination problem of photogenerated carriers, and effectively improving the spectral response, external quantum efficiency and detection rate of the device.

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

[0009] The method for preparing the window-type charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector comprises the following steps:

[0010] 1) RCA standard cleaning of silicon carbide highly doped n+ type substrate;

[0011] 2) epitaxially growing a silicon carbide n-type buffer layer on a silicon carbide highly doped n+ type substrate;

[0012] 3) epitaxially growing a silicon carbide low-doped n-layer on the silicon carbide n-type buffer layer;

[0013] 4) Using deposition, photolithography, etching, ion implantation and high temperature annealing technology to form multiple uniformly distributed small-area silicon carbide n-type charge layers in the n-layer, below the n-type charge layer is a silicon carbide low-doped n-type absorption layer, and above the n-type charge layer is a silicon carbide low-doped n-type multiplication layer;

[0014] 5) epitaxially growing a silicon carbide highly doped p+ type ohmic contact layer on the silicon carbide low doped n-type multiplication layer;

[0015] 6) using deposition, photolithography and etching techniques to etch uniformly distributed windows in the p+ type ohmic contact layer corresponding to the intervals of the separated n type charge layer;

[0016] 7) Use thermal oxidation and PECVD technology to form a wide bandgap passivation isolation layer such as silicon dioxide or hafnium oxide at the p+ type ohmic contact layer window;

[0017] 8) Photolithography, magnetron sputtering and annealing techniques are used to prepare p+ type ohmic contact electrodes and n+ type ohmic contact electrodes on the surface of the highly doped p+ type ohmic contact layer and on the bottom of the n+ type substrate, respectively.

[0018] If the charge layer doping concentration of the conventional SACM structure silicon carbide ultraviolet avalanche photodetector type in the prior art is high, it will have a certain blocking effect on the drift of photogenerated carriers, causing the detector to easily break down prematurely, and it is difficult to achieve avalanche multiplication photodetection with high spectral responsivity and quantum efficiency; if the charge layer doping concentration is low, it will reduce the modulation effect on the avalanche electric field, causing the avalanche voltage of the detector to be too high, which cannot meet the industry requirements of APD.

[0019] Compared with the prior art, the present invention has the following outstanding advantages: the window-type charge layer separation SACM structure silicon carbide ultraviolet avalanche photodetector designed by the present invention is composed of a plurality of small-area absorption layers, charge layer and multiplication layer separation (SACM) structures and a plurality of small-area in structures. The electric fields of adjacent SACM structures are interconnected and coupled. The photogenerated carriers generated in the in structure can be accelerated by the coupled electric field to drift to the n-type multiplication layer of the SACM structure. Under the acceleration of the high electric field, the carriers in the n-type multiplication layer interact with the atomic valence bonds in the lattice to produce Collision ionization is generated, thereby producing avalanche breakdown, realizing multiplication detection of weak ultraviolet signals, reducing the avalanche area while ensuring avalanche uniformity, and effectively reducing the dark current of the device; at the same time, ultraviolet light at the p+ type ohmic contact layer window can be directly incident on the n-type absorption layer, reducing the recombination problem of photogenerated carriers, and effectively improving the spectral response, external quantum efficiency and detection rate of the device. A high built-in electric field is easily generated at the edge of the p+ type ohmic contact layer window, which prompts the built-in electric field of the n-type multiplication layer to quickly reach the critical electric field of silicon carbide avalanche, effectively reducing the avalanche voltage of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a cross-sectional schematic diagram of the SACM structure silicon carbide ultraviolet avalanche photodetector with window-type charge layer separation described in an embodiment of the present invention.

[0021] Figure 2 This is a comparison diagram of the dark current of the SACM structure silicon carbide ultraviolet avalanche photodetector with windowed charge layer separation described in an embodiment of the present invention and the traditional SACM structure ultraviolet avalanche photodetector.

[0022] Figure 3 This is a comparison diagram of the spectral responsivity curves of the SACM structure silicon carbide ultraviolet avalanche photodetector with windowed charge layer separation described in an embodiment of the present invention and the traditional SACM structure ultraviolet avalanche photodetector under a reverse bias voltage of 20V.

[0023] exist Figure 1 In the figure, the markers are:

[0024] (1) Silicon carbide highly doped n+ type 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 highly doped p+ type ohmic contact layer, (7) Silicon dioxide passivation isolation layer, (8) p+ type ohmic contact electrode, (9) n+ type ohmic contact electrode. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the following embodiments will further illustrate the present invention in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] In order to make the structure of the present invention more clear and understandable, see Figure 1 A schematic cross-sectional view of a SACM structured silicon carbide ultraviolet avalanche photodetector with windowed charge layer separation according to an embodiment of the present invention.

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

[0028] A commercial silicon carbide highly doped n+ type substrate (1) may have a thickness of 50 to 800 μm and a doping concentration of 10 19 / cm 3 ~10 20 / cm 3 The longitudinal section width can be 100 to 200 μm; a silicon carbide n-type buffer layer (2) is provided on a silicon carbide highly doped n+ type substrate (1); the width of the silicon carbide n-type buffer layer (2) can be 100 to 200 μm, the thickness of the silicon carbide n-type buffer layer (2) can be 100 nm to 1 μm, and the doping concentration can be on the order of 10 18 / cm 3 ~10 19 / cm 3 ;

[0029] A silicon carbide low-doped n-type absorption layer (3) is arranged upward from the center of the silicon carbide n-type buffer layer (2); the width of the silicon carbide low-doped n-type absorption layer (3) can be 100 to 200 μm, the thickness can be 1 to 3 μm, and the doping concentration can be on the order of 10 15 / cm 3 ~10 16 / cm 3 A small area evenly distributed separated silicon carbide n-type charge layer (4) is provided in the silicon carbide low-doped n-type absorption layer (3), each separated silicon carbide n-type charge layer (4) may have a width of 5 to 10 μm, a thickness of 100 to 200 nm, and a doping concentration of 10 17 / cm 3 ~10 18 / cm 3 The width of the interval between adjacent separated silicon carbide n-type charge layers (4) can be 5 to 10 μm, and the thickness can be 100 to 200 nm; below the separated silicon carbide n-type charge layer (4) is a silicon carbide low-doped n-type absorption layer (3); above the n-type charge layer (4) is a silicon carbide low-doped n-type multiplication layer (5), and the width of the silicon carbide low-doped n-type multiplication layer (5) can be 100 to 200 μm, the thickness can be 300 to 700 nm, and the doping concentration can be on the order of 10 15 / cm 3 ~10 16 / cm 3 ; A window-type silicon carbide highly doped p+ type ohmic contact layer (6) is provided on the silicon carbide low-doped n-type multiplication layer (5) corresponding to the separated silicon carbide n-type charge layer (4); each window-type silicon carbide highly doped p+ type ohmic contact layer (6) may have a width of 5 to 10 μm, a thickness of 200 to 300 nm, and a doping concentration of 10 19 / cm 3 ~10 20 / cm 3 The width of the etching window in the adjacent window-type silicon carbide highly doped p+ type ohmic contact layer (6) can be 5 to 10 μm, and the thickness can be 200 to 300 nm; a silicon dioxide passivation isolation layer (7) is provided at the window of the window-type silicon carbide highly doped p+ type ohmic contact layer (6), and 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 to 2 μm; a p+ type ohmic contact electrode (8) is provided on the upper surface of the window-type silicon carbide highly doped p+ type ohmic contact layer (6), and an n+ type ohmic contact electrode (9) is provided on the back side of the silicon carbide highly doped n+ type substrate (1).

[0030] The entire device consists of multiple small-area absorption layers, charge layer and multiplication layer separation (SACM) structures and multiple small-area in structures. The electric fields of adjacent SACM structures are interconnected and coupled. The photogenerated carriers generated in the in structure can be accelerated by the coupled electric field to drift into the n-type multiplication layer of the SACM structure. Under the acceleration of the high electric field, the carriers in the n-type multiplication layer interact with the atomic valence bonds in the lattice to produce collision ionization, thereby producing avalanche breakdown, realizing multiplication detection of weak ultraviolet signals, and reducing the avalanche voltage and dark current of the device while ensuring avalanche uniformity; at the same time, ultraviolet light at the window of the p+ type ohmic contact layer can be directly incident on the n-type absorption layer, reducing the recombination problem of photogenerated carriers, and effectively improving the spectral response, external quantum efficiency and detection rate of the device.

[0031] The method for preparing the window-type charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector comprises the following steps:

[0032] 1) RCA standard cleaning of silicon carbide highly doped n+ type substrate;

[0033] 2) epitaxially growing a silicon carbide n-type buffer layer on a silicon carbide highly doped n+ type substrate;

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

[0035] 4) Using deposition, photolithography, etching, ion implantation and high temperature annealing technology to form multiple uniformly distributed small-area silicon carbide n-type charge layers in the n-layer, below the n-type charge layer is a silicon carbide low-doped n-type absorption layer, and above the n-type charge layer is a silicon carbide low-doped n-type multiplication layer;

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

[0037] 6) using deposition, photolithography and etching techniques to etch uniformly distributed windows in the p+ type ohmic contact layer corresponding to the intervals of the separated n type charge layer;

[0038] 7) Use thermal oxidation and PECVD technology to form a wide bandgap passivation isolation layer such as silicon dioxide or hafnium oxide at the p+ type ohmic contact layer window;

[0039] 8) Photolithography, magnetron sputtering and annealing techniques are used to prepare p+ type ohmic contact electrodes and n+ type ohmic contact electrodes on the surface of the highly doped p+ type ohmic contact layer and on the bottom of the n+ type substrate, respectively.

[0040] Specific preparation examples are given below.

[0041] 1) Perform RCA standard cleaning on the silicon carbide highly doped n+ type substrate (1) sample, the steps are as follows:

[0042] a. Ultrasonic cleaning with toluene, acetone and ethanol at least twice, then rinse with deionized water.

[0043] b. Use liquid No. 3 to boil at 250°C for 20 minutes, and rinse with hot and cold deionized water. The volume ratio of the liquid No. 3 is H2SO4:H2O2=4:1.

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

[0045] d. Boil the sample in liquid No. 1 for 10 minutes or more, and rinse with hot and cold deionized water. The liquid No. 1 has a volume ratio of NH3·H2O:H2O2:H2O=1:1:4.

[0046] e. Boil the sample in liquid No. 2 for 10 minutes or more, and rinse with hot and cold deionized water. The volume ratio of liquid No. 1 is 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 gas, 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) The doping concentration of epitaxial growth on the silicon carbide 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 techniques to form a mask, on this basis, phosphorus ions are implanted into the n-layer, high temperature annealing is performed to activate the phosphorus ions, and multiple evenly distributed small-area separated silicon carbide n-type charge layers (4) are formed in the n-layer, each separated silicon carbide n-type charge layer (4) can have a width of 5 μm to 10 μm, a thickness of 100 nm to 200 nm, and a doping concentration 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 μm to 10 μm, and the thickness can be 100 nm to 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) Epitaxial growth of a doping concentration of 10 on a low-doped n-type multiplication layer (5) of silicon carbide 19 / cm 3 ~10 20 / cm 3 , a window-type silicon carbide highly doped p+ type ohmic contact layer (6) with a width of 100 μm to 200 μm and a thickness of 200 nm to 300 nm;

[0052] 6) using deposition, photolithography and etching techniques to etch uniformly distributed windows in the window-type silicon carbide highly doped p+ type ohmic contact layer (6) corresponding to the intervals of the separated separated silicon carbide n-type charge layer (4), each window-type silicon carbide highly doped p+ type ohmic contact layer (6) having a width of 5 μm to 10 μm, a thickness of 200 nm to 300 nm, and a doping concentration of 10 19 / cm 3 ~10 20 / cm 3 , the width of the etching window in the adjacent window-type silicon carbide highly doped p+ type ohmic contact layer (6) is 5 μm to 10 μm, and the thickness is 200 nm to 300 nm;

[0053] 7) Clean the sample using RCA standard to remove impurities on the sample surface, and use dry oxygen, wet oxygen and dry oxygen to oxidize alternately to grow a layer of oxide on the positive surface of the sample (towards the upper surface of the n-type absorption layer) as a sacrificial layer; place the sample with the grown sacrificial layer in buffered hydrofluoric acid for corrosion to remove the sacrificial layer; use dry oxygen, wet oxygen, dry oxygen and nitrogen to oxidize alternately to grow a thermally oxidized silicon dioxide passivation isolation layer with a thickness of 10nm to 60nm (7). Alternatively, after removing the sacrificial layer, PECVD technology can be used to grow a wide bandgap passivation material such as silicon dioxide or hafnium oxide with a thickness of 10nm to 2μm as the silicon dioxide passivation isolation layer (7);

[0054] 8) Using a photolithography process, the photoresist is exposed and developed, and the oxide layer on the upper part of the window-type silicon carbide highly doped p+ type ohmic contact layer is etched with buffered hydrofluoric acid to form an electrode window. A layer of alloy is prepared by a magnetron sputtering process to form a p+ type ohmic contact electrode (8). A layer of photoresist is prepared on the front side of the sample for protection and isolation, and the oxide layer on the bottom side of the substrate is etched with buffered hydrofluoric acid. An alloy layer is prepared by magnetron sputtering to form an n+ type ohmic contact electrode (9). The two electrodes are annealed so that the window-type silicon carbide highly doped p+ type ohmic contact layer (8) and the n+ type ohmic contact electrode (9) of the sample form good ohmic contacts with the window-type silicon carbide highly doped p+ type ohmic contact layer (6) and the silicon carbide highly doped n+ type substrate (1), respectively.

[0055] Figure 2 This is a comparison of the dark current of the SACM structured silicon carbide ultraviolet avalanche photodetector with windowed charge layer separation described in the embodiment of the present invention and the traditional SACM structured ultraviolet avalanche photodetector. Figure 2 It can be seen that compared with the traditional SACM ultraviolet avalanche photodetector, the dark current of the SACM structure silicon carbide ultraviolet avalanche photodetector with windowed charge layer separation is reduced by 62.0% and the avalanche voltage is reduced by 13.5%.

[0056] Figure 3 This is a comparison of the spectral responsivity curves of the SACM structure silicon carbide ultraviolet avalanche photodetector with window-type charge layer separation described in the embodiment of the present invention and the traditional SACM structure ultraviolet avalanche photodetector under a reverse bias voltage of 20V. Figure 3 It can be seen that compared with the traditional SACM ultraviolet avalanche photodetector, the peak spectral responsivity of the windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector is increased by 51.0%.

[0057] The above embodiments are only preferred embodiments of the present invention and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A window-type charge layer separation SACM structure silicon carbide ultraviolet avalanche photodetector, characterized in that A silicon carbide highly doped n+ type substrate is provided from bottom to top, a silicon carbide n-type buffer layer is provided on the silicon carbide highly doped n+ type substrate, a silicon carbide low doped n- layer is provided upward from the center of the silicon carbide n-type buffer layer, a small area evenly distributed separated silicon carbide n-type charge layer is provided in the silicon carbide low doped n- layer for modulating the avalanche electric field and maintaining the uniformity of the avalanche, a silicon carbide low doped n- type absorption layer is provided below the separated silicon carbide n-type charge layer for depletion of photogenerated carriers; above the separated silicon carbide n-type charge layer The invention discloses a silicon carbide low-doped n-type multiplication layer for multiplying photogenerated carriers, wherein a window-type silicon carbide highly-doped p+-type ohmic contact layer is arranged on the silicon carbide low-doped n-type multiplication layer at a position corresponding to the separated n-type charge layer for collecting photogenerated carriers, a silicon dioxide passivation isolation layer is arranged on the window-type silicon carbide highly-doped p+-type ohmic contact layer, a p+-type ohmic contact electrode is arranged on the upper surface of the window-type silicon carbide highly-doped p+-type ohmic contact layer, and an n+-type ohmic contact electrode is arranged on the back side of the silicon carbide highly-doped n+-type substrate.

2. A windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector as claimed in claim 1, characterized in that It consists of a plurality of small-area absorption layers, charge layers and multiplication layer separation SACM structures and a plurality of small-area in structures. The electric fields of adjacent SACM structures are interconnected and coupled. The photogenerated carriers generated in the in structure are accelerated by the coupled electric field to drift to the n-type multiplication layer of the SACM structure. Under the acceleration of the high electric field, the carriers in the n-type multiplication layer interact with the atomic valence bonds in the lattice to produce collision ionization, thereby generating avalanche breakdown, realizing multiplication detection of weak ultraviolet signals, and reducing the avalanche voltage and dark current of the device while ensuring avalanche uniformity; at the same time, ultraviolet light at the window of the p+ type ohmic contact layer is directly incident on the n-type absorption layer, reducing the recombination problem of photogenerated carriers, and effectively improving the spectral response, external quantum efficiency and detection rate of the device.

3. A windowed charge layer separated SACM structure silicon carbide ultraviolet avalanche photodetector as claimed in claim 1, characterized in that The silicon carbide highly doped n+ type substrate has a width of 100 to 200 μm, a thickness of 50 to 800 μm, and a doping concentration of 10 19 / cm 3 ~10 20 / cm 3 .

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

5. The window-type charge layer separation SACM structure silicon carbide ultraviolet avalanche photodetector as claimed in claim 1, characterized in that The width of the silicon carbide low-doped n-type absorption layer is 100-200 μm, the thickness is 1-3 μm, and the doping concentration is on the order of 10 15 / cm 3 ~10 16 / cm 3 .

6. The window-type charge layer separation SACM structure silicon carbide ultraviolet avalanche photodetector as claimed in claim 1, characterized in that Each separated silicon carbide n-type charge layer has a width of 5 to 10 μm, a thickness of 100 to 200 nm, and a doping concentration of 10 17 / cm 3 ~10 18 / cm 3 The width of the interval between adjacent separated silicon carbide n-type charge layers is 5 to 10 μm, and the thickness is 100 to 200 nm.

7. The window-type charge layer separation SACM structure silicon carbide ultraviolet avalanche photodetector as claimed in claim 1, characterized in that The silicon carbide low-doped n-type multiplication layer has a width of 100 to 200 μm, a thickness of 300 to 700 nm, and a doping concentration of 10 15 / cm 3 ~10 16 / cm 3 .

8. The window-type charge layer separation SACM structure silicon carbide ultraviolet avalanche photodetector as claimed in claim 1, characterized in that Each window-type silicon carbide highly doped p+ type ohmic contact layer has a width of 5 to 10 μm, a thickness of 200 to 300 nm, and a doping concentration of 10 19 / cm 3 ~10 20 / cm 3 The width of the etching window in the adjacent window-type silicon carbide highly doped p+ type ohmic contact layer is 5 to 10 μm, and the thickness is 200 to 300 nm.

9. The window-type charge layer separation SACM structure silicon carbide ultraviolet avalanche photodetector as claimed in claim 1, characterized in that A silicon dioxide passivation isolation layer is provided at the window of each windowed silicon carbide highly doped p+ type ohmic contact layer. The silicon dioxide passivation isolation layer can also be replaced by a wide bandgap passivation isolation material such as hafnium oxide, and the thickness can be 10nm to 2μm.

10. The method for preparing a window-type charge layer separation SACM structure silicon carbide ultraviolet avalanche photodetector as claimed in claim 1, characterized in that The following steps are involved: 1) RCA standard cleaning of silicon carbide highly doped n+ type substrate; 2) epitaxially growing a silicon carbide n-type buffer layer on a silicon carbide highly doped n+ type substrate; 3) epitaxially growing a silicon carbide low-doped n-layer on the silicon carbide n-type buffer layer; 4) Using deposition, photolithography, etching, ion implantation and high temperature annealing technology to form multiple uniformly distributed small-area silicon carbide n-type charge layers in the n-layer, below the n-type charge layer is a silicon carbide low-doped n-type absorption layer, and above the n-type charge layer is a silicon carbide low-doped n-type multiplication layer; 5) epitaxially growing a silicon carbide highly doped p+ type ohmic contact layer on the silicon carbide low doped n-type multiplication layer; 6) using deposition, photolithography and etching techniques to etch uniformly distributed windows in the p+ type ohmic contact layer corresponding to the intervals of the separated n type charge layer; 7) Use thermal oxidation and PECVD technology to form a wide bandgap passivation isolation layer such as silicon dioxide or hafnium oxide at the p+ type ohmic contact layer window; 8) Photolithography, magnetron sputtering and annealing techniques are used to prepare p+ type ohmic contact electrodes and n+ type ohmic contact electrodes on the surface of the highly doped p+ type ohmic contact layer and on the bottom of the n+ type substrate, respectively.

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