Planar avalanche single-photon detector based on recombination current suppression mechanism and manufacturing method of planar avalanche single-photon detector

Abstract

The invention relates to a planar avalanche single-photon detector based on a recombination current suppression mechanism and a manufacturing method thereof. The planar avalanche single-photon detector based on the recombination current suppression mechanism comprises a buffer layer, a P-type layer and an N-type layer which are grown on a substrate in sequence from bottom to top, the N-type layer is non-uniformly doped N-type tellurium-cadmium-mercury, and the doping is in Gaussian distribution; photons are incident from the substrate, the cathode leading-out end on the P-type layer is connected with the cathode of the power supply, the anode leading-out end on the N-type layer is connected with the anode of the power supply, and the photons are absorbed by the P-type layer and the N-type layer and multiplied at the interface of the P-type layer and the N-type layer. The invention has the advantages of simple process and compact design, and can greatly reduce dark current and improve gain in a high-temperature working environment.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric detectors, and in particular to a planar avalanche single-photon detector based on a composite current suppression mechanism and a manufacturing method thereof. Background Art

[0002] The mid-wave infrared (MWIR) band (3-5 microns) is very important in detecting high temperature sources (such as fires and volcanoes) and resisting background radiation interference, so it is of great significance in space-to-ground communications and civilian remote sensing scenarios. Traditional photoconductive devices and PN junctions are often unable to perform these tasks due to limited gain and sensitivity. In contrast, avalanche photodiodes (APDs) use the avalanche multiplication process to generate multiple electron-hole pairs from a single photon, greatly improving the detection sensitivity and making them particularly suitable for weak signal detection.

[0003] HgCdTe (MCT) APDs are seen as a promising option due to their tunable response bandwidth, high quantum efficiency, and sensitivity in the MWIR range. Nevertheless, conventional MCT APDs face some challenges, especially under high-temperature operation. In order to reduce the dark current, which increases exponentially with temperature, MCT APDs usually need to operate at low temperatures (about 77K). Moreover, the ionization coefficients of electrons and holes in MCT APDs are quite different, resulting in high dark current and low noise at high bias and high temperature.

[0004] When operating under high temperature conditions, the dark current of APDs increases and the gain decreases, which is critical for weak signal detection in practical applications. This problem is particularly evident in MCT APDs because the dominant mechanisms affecting dark current, such as Shockley-Read-Hall recombination and avalanche effect, are very significant at high temperatures. The increase in dark current not only reduces the signal-to-noise ratio, but also requires more complex cooling schemes, thus limiting the practicality and deployment of these devices in real-world scenarios. Summary of the invention

[0005] The purpose of the present invention is to provide a planar avalanche single photon detector based on the mechanism of suppressing recombination current and a method for manufacturing the same, which overcomes the shortcomings of the prior art that the dark current of the APD increases and the gain decreases when working under high temperature conditions.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] A planar avalanche single-photon detector based on a mechanism of suppressing a recombination current comprises a substrate, a buffer layer, a P-type layer, an N-type layer, a passivation layer, a cathode lead terminal, and an anode lead terminal.

[0008] A buffer layer is arranged on the substrate, a P-type layer is arranged on the buffer layer, and an N-type layer is inlaid in the center of the P-type layer; a cathode lead-out terminal is arranged at the outer edge of the P-type layer, an anode lead-out terminal is arranged in the center of the N-type layer, and a passivation layer is covered between the cathode lead-out terminal and the anode lead-out terminal;

[0009] The P-type layer is P-type HgCdTe doped with Hg vacancies, and the N-type layer is N-type HgCdTe doped non-uniformly. The doping presents a Gaussian distribution, and the doping concentration transitions from a high content at the center of the N-type layer surface to a low content at the interface between the N-type layer and the P-type layer.

[0010] The substrate is made of cadmium zinc telluride or gallium arsenide or cadmium telluride or silicon material.

[0011] The buffer layer is made of cadmium telluride and has a thickness ranging from 0.8 to 1.2 μm.

[0012] The thickness of the P-type layer ranges from 5 to 8 μm, and the doping concentration is 5×10 15 ~5×10 16 cm -3 ; N-type layer (thickness range is 1μm to 3μm, doping concentration is 5×10 14 ~1×10 17 cm -3 .

[0013] The passivation layer is a double-layer film made of cadmium telluride and zinc sulfide. The cadmium telluride film is arranged on the zinc sulfide film, and the thickness ratio of the cadmium telluride film to the zinc sulfide film is 1:3.

[0014] The cathode lead-out terminal is a double-layer electrode of Cr and Au, Cr is the ohmic contact layer of the lower layer, and Au is the metal conductive layer of the upper layer; or, the cathode lead-out terminal is a double-layer electrode of Sn and Au, Sn is the ohmic contact layer of the lower layer, and Au is the metal conductive layer of the upper layer;

[0015] The anode lead-out terminal is a double-layer electrode of Cr and Au, Cr is the lower ohmic contact layer, and Au is the upper metal conductive layer; or, the anode lead-out terminal is a double-layer electrode of Sn and Au, Sn is the lower ohmic contact layer, and Au is the upper metal conductive layer.

[0016] The thickness of Cr or Sn is 0.01 to 0.1 μm, and the thickness of Au is 0.1 to 0.6 μm.

[0017] The manufacturing method of the planar avalanche single-photon detector based on the mechanism of suppressing recombination current is as follows:

[0018] Step 1, growing a 0.8-1.2 μm cadmium telluride buffer layer on the substrate;

[0019] Step 2: Using liquid phase epitaxial growth technology to accurately grow a P-type layer on the buffer layer;

[0020] Step 3: Boron ion implantation is performed in the P-type layer, and Hg vacancies are suppressed by annealing to form an N-type layer in the center of the P-type layer, so that the doping concentration presents a Gaussian distribution;

[0021] Step 4: growing a zinc sulfide film and a cadmium telluride film on the surface of the P-type layer and the N-type layer in sequence to form a passivation layer, wherein the thickness ratio of the cadmium telluride film to the zinc sulfide film is 1:3;

[0022] Step 5, using hydrochloric acid and dichromic acid solution to remove the double-layer passivation film material at the electrode hole position;

[0023] Step six, using vacuum magnetron sputtering to grow cathode lead-out terminals and anode lead-out terminals, forming a Cr and Au double-layer electrode, or a Sn and Au double-layer electrode, with a thickness of 20 to 200 nm, forming a good gold semi-contact with mercury cadmium telluride.

[0024] The substrate in step 1 is made of cadmium zinc telluride, gallium arsenide, cadmium telluride or silicon material.

[0025] The Gaussian distribution of the doping concentration in step 3 is a transition of the doping concentration from a high concentration at the center of the surface of the N-type layer to a low concentration at the interface between the N-type layer and the P-type layer.

[0026] The beneficial effects of the present invention are as follows: a new structure for suppressing recombination current is proposed, and a Gaussian distribution of doping concentration is achieved in the N-type region. The Gaussian distribution of the N-type layer effectively separates the recombination region from the collision ionization region, and keeps the collision ionization region away from the junction of the P-type layer and the N-type layer, so that the device can not only reduce the dark current by suppressing the recombination current under high operating temperature conditions, but also avoid the excess gain generated by the loss of photoelectrons for avalanche. A lower dark current and higher optical gain are achieved, which can meet the requirements of 160K operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the cross-sectional structure of the present invention;

[0028] Figure 2 It is a top view of the structure of the present invention;

[0029] Figure 3 It is the relationship between the dark current and voltage of the planar avalanche single photon detector of the present invention, and the ordinate is the ordinary coordinate;

[0030] Figure 4 is the relationship between the gain and voltage of the planar avalanche single photon detector of the present invention, and the ordinate is the ordinary coordinate;

[0031] In the figure: 1-substrate; 2-buffer layer; 3-P-type layer; 4-N-type layer; 5-passivation layer; 6-cathode lead terminal; 7-anode lead terminal. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings, which are only used for exemplary description and cannot be understood as limiting the present invention.

[0033] In order to more concisely describe the present embodiment, some parts known to those skilled in the art but not related to the main content of the present invention are omitted in the drawings or descriptions. In addition, for the convenience of description, some parts in the drawings are omitted, enlarged or reduced, but they do not represent the size or entire structure of the actual product.

[0034] The present invention discloses a planar avalanche single-photon detector based on the mechanism of suppressing composite current, comprising a substrate 1, a buffer layer 2, a P-type layer 3, an N-type layer 4, a passivation layer 5, a cathode lead terminal 6, and an anode lead terminal 7.

[0035] like Figure 1 As shown, a buffer layer 2 made of cadmium telluride is arranged on a substrate 1 made of cadmium zinc telluride or gallium arsenide or cadmium telluride or silicon material, and the thickness of the buffer layer 2 is in the range of 0.8-1.2 μm.

[0036] A P-type layer 3 is disposed on the buffer layer 2, and an N-type layer 4 is embedded in the center of the P-type layer 3;

[0037] The P-type layer 3 is a P-type HgCdTe doped with Hg vacancies. The thickness of the P-type layer 3 is in the range of 5 to 8 μm, the Cd component is 0.3, and the doping concentration is 5×10 15 ~5×10 16 cm -3 .

[0038] The N-type layer 4 is non-uniformly doped N-type HgCdTe, the thickness of the N-type layer 4 is in the range of 1 μm to 3 μm, the Cd component is 0.3, and the doping concentration is 5×10 14 ~1×10 17 cm -3 The doping presents a Gaussian distribution, and the doping concentration transitions from a high content at the center of the surface of the N-type layer 4 to a low content at the interface between the N-type layer 4 and the P-type layer 3. Because the N-type layer 4 is formed in the center of the P-type layer 3 by boron ion implantation, and the boron ion implantation site is located in the center of the formed N-type layer 4, where the doping content is the highest, the doping concentration transitions from a high content at the center of the surface of the N-type layer 4 at the boron ion implantation site to a low content at the interface between the N-type layer 4 and the P-type layer 3.

[0039] The passivation layer 5 is a double-layer film made of cadmium telluride and zinc sulfide, the cadmium telluride film is arranged on the zinc sulfide film, and the thickness ratio of the cadmium telluride film to the zinc sulfide film is 1:3; Figure 2 As shown, a cathode lead-out terminal 6 is arranged at the outer edge of the P-type layer 3, an anode lead-out terminal 7 is arranged at the center of the N-type layer 4, and a passivation layer 5 is covered between the cathode lead-out terminal 6 and the anode lead-out terminal 7.

[0040] The cathode lead-out terminal 6 is a double-layer electrode of Cr and Au, Cr is the ohmic contact layer of the lower layer, and Au is the metal conductive layer of the upper layer; or, the cathode lead-out terminal 6 is a double-layer electrode of Sn and Au, Sn is the ohmic contact layer of the lower layer, and Au is the metal conductive layer of the upper layer;

[0041] The anode lead terminal 7 is a double-layer electrode of Cr and Au, Cr is the ohmic contact layer of the lower layer, and Au is the metal conductive layer of the upper layer; or, the anode lead terminal 7 is a double-layer electrode of Sn and Au, Sn is the ohmic contact layer of the lower layer, and Au is the metal conductive layer of the upper layer. The thickness of Cr or Sn is 0.01-0.1 μm, and the thickness of Au is 0.1-0.6 μm.

[0042] The manufacturing method of the planar avalanche single-photon detector based on the mechanism of suppressing recombination current is as follows:

[0043] Step 1: growing a 0.8-1.2 μm cadmium telluride buffer layer 2 on a substrate 1 made of cadmium zinc telluride, gallium arsenide, cadmium telluride or silicon material;

[0044] Step 2: Using liquid phase epitaxial growth technology, a P-type layer (3) is precisely grown on the buffer layer 2. The thickness of the P-type layer is 8 μm and the doping concentration is 1×10 16 cm -3 .

[0045] Step 3: Boron ion implantation is performed in the P-type layer 3, and Hg vacancies are suppressed by annealing to form an N-type layer 4 in the center of the P-type layer 3, so that the doping concentration presents a Gaussian distribution, and the doping concentration transitions from the high content in the center of the surface of the N-type layer 4 where the boron ions are implanted to the low content at the interface between the N-type layer 4 and the P-type layer 3. The doping concentration at the top boundary is 7×10 16 cm -3 .

[0046] Step 4: zinc sulfide film and cadmium telluride film are grown on the surface of the P-type layer 3 and the N-type layer 4 in sequence to form a passivation layer 5. The thickness ratio of the cadmium telluride film to the zinc sulfide film is 1:3, and the thicknesses of the zinc sulfide and cadmium telluride are 50 nm and 150 nm, respectively.

[0047] Step 5, using hydrochloric acid and dichromic acid solution to remove the double-layer passivation film material at the electrode hole position;

[0048] Step 6: Use vacuum magnetron sputtering to grow the cathode lead terminal (6) and the anode lead terminal (7) to form a Cr and Au double-layer electrode, or a Sn and Au double-layer electrode, with a thickness of 20 to 200 nm. Cr or Sn serves as the lower ohmic contact layer in contact with the P-type layer 3 and the N-type layer 4, and Au serves as the upper metal conductive layer to form a good gold semi-contact with the mercury cadmium telluride.

[0049] like Figure 3 The figure shows the relationship between the dark current and voltage of the planar avalanche single photon detector of the present invention at 160K. Its dark current at -8 volts is 5.51×10 -7 ampere.

[0050] like Figure 4 FIG. 1 is a graph showing the relationship between the gain and voltage of the planar avalanche single photon detector of the present invention at 160 K. Its gain at -8 volts is 1812.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. That is, any equivalent changes and modifications made according to the content of the patent application scope of the present invention should be within the technical scope of the present invention.

Claims

1. A planar avalanche single-photon detector based on a recombination current suppression mechanism, comprising a substrate (1), a buffer layer (2), a P-type layer (3), an N-type layer (4), a passivation layer (5), a cathode lead terminal (6), and an anode lead terminal (7), characterized in that: A buffer layer (2) is arranged on a substrate (1), a P-type layer (3) is arranged on the buffer layer (2), and an N-type layer (4) is embedded in the center of the P-type layer (3); a cathode lead-out terminal (6) is arranged at the outer edge of the P-type layer (3), an anode lead-out terminal (7) is arranged in the center of the N-type layer (4), and a passivation layer (5) is covered between the cathode lead-out terminal (6) and the anode lead-out terminal (7); The P-type layer (3) is P-type mercury cadmium telluride doped with Hg vacancies, and the N-type layer (4) is N-type mercury cadmium telluride doped inhomogeneously, wherein the doping presents a Gaussian distribution, and the doping concentration transitions from a high content at the center of the surface of the N-type layer (4) to a low content at the interface between the N-type layer (4) and the P-type layer (3).

2. The planar avalanche single-photon detector based on the recombination current suppression mechanism according to claim 1, characterized in that: The substrate (1) is made of cadmium zinc telluride, gallium arsenide, cadmium telluride or silicon material.

3. The planar avalanche single-photon detector based on the recombination current suppression mechanism according to claim 1, characterized in that: The buffer layer (2) is made of cadmium telluride and has a thickness ranging from 0.8 to 1.2 μm.

4. The planar avalanche single-photon detector based on the suppression of recombination current mechanism according to claim 1, characterized in that: The thickness of the P-type layer (3) is in the range of 5 to 8 μm, and the doping concentration is 5×10 15 ~5×10 16 cm -3 The thickness of the N-type layer (4) is in the range of 1 μm to 3 μm, and the doping concentration is 5×10 14 ~1×10 17 cm -3 .

5. The planar avalanche single-photon detector based on the recombination current suppression mechanism according to claim 1, characterized in that: The passivation layer (5) is a double-layer film made of cadmium telluride and zinc sulfide, the cadmium telluride film is arranged on the zinc sulfide film, and the thickness ratio of the cadmium telluride film to the zinc sulfide film is 1:

3.

6. The planar avalanche single-photon detector based on the recombination current suppression mechanism according to claim 1, characterized in that: The cathode lead-out terminal (6) is a double-layer electrode of Cr and Au, Cr is an ohmic contact layer at the bottom layer, and Au is a metal conductive layer at the top layer; or, the cathode lead-out terminal (6) is a double-layer electrode of Sn and Au, Sn is an ohmic contact layer at the bottom layer, and Au is a metal conductive layer at the top layer; The anode lead-out terminal (7) is a double-layer electrode of Cr and Au, Cr is the lower ohmic contact layer, and Au is the upper metal conductive layer; or, the anode lead-out terminal (7) is a double-layer electrode of Sn and Au, Sn is the lower ohmic contact layer, and Au is the upper metal conductive layer.

7. The planar avalanche single-photon detector based on the recombination current suppression mechanism according to claim 6, characterized in that: The thickness of Cr or Sn is 0.01 to 0.1 μm, and the thickness of Au is 0.1 to 0.6 μm.

8. The method for manufacturing a planar avalanche single-photon detector based on the mechanism of suppressing recombination current according to any one of claims 1 to 6, characterized in that: The production steps are as follows: Step 1: growing a 0.8-1.2 μm cadmium telluride buffer layer (2) on a substrate (1); Step 2: Using liquid phase epitaxial growth technology to precisely grow a P-type layer (3) on the buffer layer (2); Step 3: implanting boron ions into the P-type layer (3), suppressing Hg vacancies by annealing, forming an N-type layer (4) in the center of the P-type layer (3), and achieving a Gaussian distribution of doping concentration; Step 4: growing a zinc sulfide film and a cadmium telluride film on the surface of the P-type layer (3) and the N-type layer (4) in sequence to form a passivation layer (5), wherein the thickness ratio of the cadmium telluride film to the zinc sulfide film is 1:3; Step 5, using hydrochloric acid and dichromic acid solution to remove the double-layer passivation film material at the electrode hole position; Step 6: Use vacuum magnetron sputtering to grow the cathode lead terminal (6) and the anode lead terminal (7) to form a Cr and Au double-layer electrode, or a Sn and Au double-layer electrode, with a thickness of 20 to 200 nm, to form a good gold semi-contact with the mercury cadmium telluride.

9. The method for manufacturing a planar avalanche single-photon detector based on the recombination current suppression mechanism according to claim 8, characterized in that: The substrate (1) in step 1 is made of cadmium zinc telluride, gallium arsenide, cadmium telluride or silicon material.

10. The method for manufacturing a planar avalanche single-photon detector based on the recombination current suppression mechanism according to claim 8, characterized in that: The Gaussian distribution of the doping concentration in step 3 is a transition of the doping concentration from a high concentration at the center of the surface of the N-type layer (4) to a low concentration at the interface between the N-type layer (4) and the P-type layer (3).

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