Dumping type linear single photon avalanche detector and preparation method

Abstract

The invention relates to the technical field of photoelectric detectors, in particular to a dumping type linear single-photon avalanche detector which comprises a substrate, an N electrode, an N contact layer, an N multiplication layer, a P absorption layer and a P electrode. The substrate is located at the bottom of the detector. On the substrate, the N electrode, the N contact layer, the N multiplication layer, the P absorption layer and the P electrode are consistent in height and are transversely arranged in sequence. The N electrode is connected to the N contact layer, the N contact layer is connected to the N multiplication layer, the N multiplication layer is connected to the P absorption layer, and the P electrode is connected to the P absorption layer. The doping concentration of the N contact layer is larger than that of the N multiplication layer. And a transverse PN junction is formed between the P absorption layer and the N multiplication layer. The invention also comprises a preparation method. The single-photon sensitive avalanche detector solves the problem that a side electric field of an existing planar junction device influences tunneling current, the parasitic series resistance is remarkably reduced, the response bandwidth and multiplication gain of the device are improved, and the single-photon sensitive avalanche detector with wide spectral response, high time resolution, low dark current and high gain can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of photodetectors, in particular to an inclined linear single photon avalanche detector and a preparation method thereof. Background Art

[0002] Single photon avalanche detectors (SPADs) achieve electrical signal output with single photon level sensitivity under high electric fields and are widely used in various fields, including lidar (LiDAR), quantum communication and quantum measurement, deep space exploration, biological imaging, etc. Currently, SPADs mainly operate in Geiger mode combined with peripheral quenching circuits. Typical materials include (1) III-V materials such as Si / Ge, InGaAs / InP, InGaAs / InAlAs, etc., which mainly operate in the short wavelength range at room temperature or near room temperature. Dark counts, afterpulses, etc. are the main limiting factors at present; (2) Superconducting nanowire SNSPDs can cover a relatively wide spectral range, have extremely high sensitivity but usually operate at 4K or lower temperature.

[0003] Mercury cadmium telluride (Hg 1-x Cd x Te) avalanche detectors, as the most mature avalanche detectors currently, have characteristics such as pure electron impact ionization, high exponential gain, and low excess noise, and are one of the best choices for realizing linear mode single photon avalanche detectors. However, currently, typical planar HgCdTe avalanche detectors are restricted by large series resistance, two-dimensional side electric fields, etc. Issues such as the avalanche detector device being unable to operate at large bias voltages, obvious tunneling currents, and gains less than 2000 limit the development of HgCdTe avalanche detectors towards high gain, low noise, and single photon level detection. Summary of the Invention

[0004] The purpose of the present invention is to provide an inclined linear single photon avalanche detector and a preparation method thereof, mainly to solve the problems existing in the above-mentioned prior art. It can solve the large series resistance and two-dimensional side electric fields of the planar device of mercury cadmium telluride avalanche photodiodes, and realize a linear mode single photon avalanche detector with high exponential gain (>10 4 ), low dark current, low time jitter, and single photon level resolution.

[0005] To achieve the above object, the technical solution adopted by the present invention is to provide a tilting linear single-photon avalanche detector, which is characterized in that it includes a substrate, an N electrode, an N contact layer, an N multiplication layer, a P absorption layer, and a P electrode; the substrate is located at the bottom of the detector; above the substrate, the N electrode, the N contact layer, the N multiplication layer, the P absorption layer, and the P electrode are of the same height and are arranged horizontally in sequence; the N electrode is connected to the N contact layer, the N contact layer is connected to the N multiplication layer, the N multiplication layer is connected to the P absorption layer, and the P electrode is connected to the P absorption layer; the doping concentration of the N contact layer is greater than that of the N multiplication layer; a lateral PN junction is formed between the P absorption layer and the N multiplication layer.

[0006] Further, the material of the substrate is cadmium zinc telluride; the material of the P absorption layer is mercury cadmium telluride, and the cadmium component is between 0.2 and 0.45.

[0007] Further, the substrate is undoped; the doping concentration in the P absorption layer is greater than 1×10 16 / cm 3 ; the doping concentration in the N contact layer is greater than 1×10 17 / cm 3 ; the doping concentration in the N multiplication layer is less than 1×10 15 / cm 3 .

[0008] Further, the thickness of the P absorption layer is 3 to 10 microns, the width of the N contact layer is 1 to 5 microns; the width of the N multiplication layer is 2 to 15 microns.

[0009] This aspect also discloses a preparation method for manufacturing the above-mentioned tilting linear single-photon avalanche detector, which is characterized in that it includes the steps:

[0010] Step S1, using vertical liquid phase epitaxy technology on the top of the substrate to form an epitaxial growth layer;

[0011] Step S2, performing interdiffusion annealing treatment on the whole material to generate a composition gradient layer with a longitudinal distribution in the epitaxial growth layer;

[0012] Step S3, doping the composition gradient layer to form the P absorption layer;

[0013] For the composition gradient layer, doping is carried out by the method of gold doping or annealing to form the hole-doped P absorption layer;

[0014] Step S4: From the top layer of the epitaxial growth layer, dry etching is used to etch the first groove and the second groove from top to bottom, and the depth penetrates the epitaxial growth layer to reach the top of the substrate; the first groove forms an ion implantation hole corresponding to the N electrode; the second groove forms a common electrode hole corresponding to the P electrode.

[0015] Step S5: In the ion implantation hole, ion implantation is performed to form the laterally distributed N contact layer.

[0016] Step S6: Annealing and diffusion treatment is performed on the overall material, so as to form an N multiplication layer laterally outside the N contact layer; the N multiplication layer contacts the P absorption layer.

[0017] Step S7: Metal deposition is performed in the ion implantation hole and the common electrode hole; then the N electrode is formed on the ion implantation hole where metal deposition is completed, and the P electrode is formed on the common electrode hole where metal deposition is completed.

[0018] Further, in step S1, the epitaxial growth layer includes a mercury cadmium telluride material in contact with the substrate in the lower layer and a cadmium telluride material on the surface.

[0019] Further, in step S2, the temperature of the interdiffusion annealing treatment is 300 to 500 degrees Celsius, and the annealing time is 1 to 48 hours.

[0020] Further, in step S4, the power of the inductively coupled plasma for the dry etching is 500 to 1500 watts, the radio frequency power is 10 to 50 watts, the argon gas flow rate is less than or equal to 20 standard milliliters per minute, the hydrogen gas flow rate is less than or equal to 25 standard milliliters per minute, the methane gas flow rate is less than or equal to 25 standard milliliters per minute, and the time is 1 to 120 minutes.

[0021] Further, in step S5, the size of the ion implantation hole is 5 to 20 micrometers; boron ion implantation is used for the ion implantation, the energy of the boron ions is 120 to 180 keV, the dose is 1×10 13 to 1×10 15 cm -2 , and the beam current is 50 to 200 microamperes.

[0022] Further, in step S6, in the annealing and diffusion treatment, the diffusion annealing temperature is 150 to 250 degrees Celsius, and the time is 120 to 250 seconds.

[0023] In view of the above technical features, the present invention provides a toppling linear single-photon avalanche detector and a preparation method thereof. The mercury cadmium telluride material is ingeniously separated through dry etching, and a lateral junction distributed avalanche detector structure is formed by ion implantation and annealing processes. Compared with the prior art, it has the following remarkable advantages:

[0024] 1. The toppling linear single-photon avalanche detector of the present invention solves the influence of the side electric field of the existing planar junction device on the tunneling current, significantly reduces the parasitic series resistance, and improves the response bandwidth and operating bias voltage of the device. The toppling structure achieves a major breakthrough, and a single-photon sensitive avalanche detector device with wide spectral response, high time resolution, low dark current, and high gain can be realized.

[0025] 2. The preparation method of the toppling linear single-photon avalanche detector of the present invention has clear principles, simple processes, convenient operations, intuitive judgment results, and great market application potential. It helps to promote the development of the single-photon detection market and the rise of more industrial applications. Brief Description of the Drawings

[0026] Figure 1 is a schematic structural diagram of a preferred embodiment of the toppling linear single-photon avalanche detector of the present invention;

[0027] Figure 2 is a graph showing the variation of exponential gain with bias voltage of a preferred embodiment of the toppling linear single-photon avalanche detector of the present invention;

[0028] Figure 3 is a single-photon pulse response diagram of a preferred embodiment of the toppling linear single-photon avalanche detector of the present invention;

[0029] Figure 4 is a single-photon counting curve diagram of a preferred embodiment of the toppling linear single-photon avalanche detector of the present invention;

[0030] Figure 5 is a method flow chart of a preferred embodiment of the preparation method of the toppling linear single-photon avalanche detector of the present invention.

[0031] In the figure: 1 - substrate, 2 - P absorption layer, 3 - N multiplication layer, 4 - N contact layer, 5 - N electrode, 6 - P electrode, 7 - ion implantation hole, 8 - common electrode hole. Detailed Embodiments

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0033] Please refer to Figure 1 , the present invention discloses an inclined linear single photon avalanche detector. As shown in the figure, in a preferred embodiment thereof, it includes a substrate 1, an N electrode 5, an N contact layer 4, an N multiplication layer 3, a P absorption layer 2, and a P electrode 6.

[0034] The substrate 1 is located at the bottom of the detector and is made of undoped cadmium zinc telluride. Other structures are fabricated on the substrate 1. Different from conventional avalanche detectors, in this embodiment, the PN junction forming the avalanche diode is horizontally distributed. That is, above the substrate 1, the N contact layer 4, the N multiplication layer 3, and the P absorption layer 2 are arranged horizontally in sequence and have the same height. The width of the N contact layer 4 is 1 to 5 micrometers. The width of the N multiplication layer 3 is 2 to 15 micrometers, and one side of it is connected to the N multiplication layer 4, and the other side is connected to the P absorption layer 2. Among them, the doping concentration of the N contact layer 4 is greater than that of the N multiplication layer 3. Specifically, the electron concentration in the N contact layer 4 is greater than 1×10 17 / cm 3 , while the electron concentration in the N multiplication layer 3 is less than 1×10 15 / cm 3 . The material of the P absorption layer 2 is mercury cadmium telluride, where the cadmium component is between 0.2 and 0.45, and the thickness is 3 to 10 micrometers. The hole concentration in the P absorption layer 2 is greater than 1×10 16 / cm 3 . The N multiplication layer 3 and the P absorption layer 2 are in contact to form a horizontal PN junction. The N electrode 5 is connected to the N contact layer 4, and the P electrode 6 is connected to the P absorption layer 2, which are used to establish an ohmic contact between the horizontal PN junction and the external circuit.

[0035] An inclined linear single photon avalanche detector of the present invention, based on the inclined linear single photon avalanche detector, due to the distribution of the horizontal vertical junction, completely suppresses the influence brought by the two-dimensional electric field tunneling current, realizes a larger working bias voltage and gain, and achieves single photon detection sensitivity. By performing a gain test on the avalanche detector at liquid nitrogen temperature. Refer to Figure 2 for the gain versus bias voltage curve, the device achieves a gain exceeding 10000 in the linear mode. For the pulsed single photon incident device of the present invention, the device achieves single photon detection sensitivity at high gain. Refer to Figure 3 for the pulsed response curve of single photons in Figure 4 and the single photon counting curve in

[0036] Please refer to Figure 1 and Figure 5 , the present invention also discloses a preparation method for manufacturing the above-mentioned inclined linear single photon avalanche detector, which is characterized by including the steps:

[0037] Step S100, epitaxial growth.

[0038] On top of the undoped cadmium zinc telluride substrate 1, mercury cadmium telluride material is epitaxially grown using vertical liquid phase epitaxy technology, where the tellurium component is between 0.2 and 0.45. Then, cadmium telluride material is epitaxially grown again above the mercury cadmium telluride material to form a complete epitaxial growth layer. The PN junction of the avalanche detector is formed in the epitaxial growth layer in subsequent steps.

[0039] Step S200, interdiffusion annealing.

[0040] The overall material that has completed epitaxial growth is subjected to interdiffusion annealing treatment. Since there are differences in the cadmium components between the cadmium telluride on the surface of the epitaxial growth layer and the cadmium zinc telluride substrate material and the mercury cadmium telluride material inside the epitaxial growth layer, interdiffusion occurs inside the epitaxial growth layer during annealing, and finally a composition gradient layer with a longitudinal distribution is formed in the middle of the epitaxial growth layer. In the interdiffusion annealing treatment, the temperature used is 300 to 500 degrees Celsius, and the annealing time is 1 to 48 hours.

[0041] Step S300, P-type doping.

[0042] In the composition gradient layer, P-type doping is carried out so that the final hole concentration is greater than 1×10 16 / cm 3 .

[0043] In this embodiment, for the composition gradient layer, doping is carried out by the method of gold doping, that is, gold elements are doped from the surface of the composition gradient layer to form a hole-doped P absorption layer 2.

[0044] In other embodiments, annealing can also be used for doping, that is, the overall material is annealed again to form a hole-doped P absorption layer 2.

[0045] Step S400, etching grooves.

[0046] Two grooves are etched from the top layer of the epitaxial growth layer, and the depth penetrates the epitaxial growth layer until the top of the substrate. The first groove serves as the ion implantation hole 7 for subsequent N-region fabrication and is also used to lead out the N electrode 5 after the N-region fabrication is completed. The size of the ion implantation hole 7 is 5 to 20 microns. The second groove is used to lead out the P electrode 6 in the P region. Since in the entire detector, the P electrodes 6 are connected together as a common electrode, the second groove also serves as the common electrode hole 8.

[0047] The etching process uses dry etching, where the power of the inductively coupled plasma for dry etching is 500 to 1500 watts, the radio frequency power is 10 to 50 watts, the argon gas flow rate is less than or equal to 20 standard milliliters per minute, the hydrogen gas flow rate is less than or equal to 25 standard milliliters per minute, the methane gas flow rate is less than or equal to 25 standard milliliters per minute, and the time is 1 to 120 minutes.

[0048] Step S500, ion implantation.

[0049] Using the ion implantation hole 7, perform an ion implantation operation, so that ions diffuse into the epitaxial growth layer along the side of the ion implantation hole 7, and finally form a laterally distributed N contact layer 4.

[0050] In the ion implantation operation, boron ions are implanted. The energy of the boron ions is 120 to 180 keV, the dose is 1×10 13 to 1×10 15 cm -2 , and the beam current is 50 - 200 μA.

[0051] Step S600, annealing and junction pushing.

[0052] After the ion implantation is completed, anneal the overall material again. The purpose of this annealing treatment is to redistribute the implanted boron ions, and then form a laterally distributed N multiplication layer 3 outside the N contact layer 4. One side of the N multiplication layer 3 is the N contact layer 4, and the other side is in contact with the P absorption layer 2 at the same time, and a PN junction is formed on the contact surface. In the annealing and junction pushing process, the junction pushing annealing temperature is 150 to 250 °C, and the time is 120 to 250 seconds.

[0053] Step S700, fabricating electrodes.

[0054] The N electrode 5 is located in the N region and is led out through the ion implantation hole 7. The P electrode 6 is led out through the common electrode hole 8. Specifically, metal deposition is performed in the ion implantation hole 7 and the common electrode hole 8, and then the N electrode 5 is formed on the ion implantation hole 7 where the metal deposition is completed, and the P electrode 6 is formed on the common electrode hole 8 where the metal deposition is completed.

[0055] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied to other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A tilting linear single-photon avalanche detector, characterized in that It includes a substrate, an N electrode, an N contact layer, an N multiplication layer, a P absorption layer, and a P electrode; the substrate is located at the bottom of the detector; above the substrate, the N electrode, the N contact layer, the N multiplication layer, the P absorption layer, and the P electrode have the same height and are arranged horizontally in sequence; The N electrode is connected to the N contact layer, the N contact layer is connected to the N multiplication layer, the N multiplication layer is connected to the P absorption layer, and the P electrode is connected to the P absorption layer; the doping concentration of the N contact layer is greater than that of the N multiplication layer; A lateral PN junction is formed between the P absorption layer and the N multiplication layer.

2. The toppling linear single-photon avalanche detector according to claim 1, wherein The material of the substrate is cadmium zinc telluride; the material of the P absorption layer is mercury cadmium telluride, where the cadmium component is between 0.2 and 0.

45.

3. The toppling linear single-photon avalanche detector according to claim 1, wherein The substrate is undoped; the doping concentration in the P absorption layer is greater than 1×10 16 / cm 3 ; the doping concentration in the N contact layer is greater than 1×10 17 / cm 3 ; the doping concentration in the N multiplication layer is less than 1×10 15 / cm 3 .

4. The toppling linear single-photon avalanche detector according to claim 1, wherein The thickness of the P absorption layer is 3 to 10 microns, the width of the N contact layer is 1 to 5 microns; the width of the N multiplication layer is 2 to 15 microns.

5. A preparation method for manufacturing the pour-type linear single-photon avalanche detector according to any one of claims 1 to 4, characterized in that, It includes steps: Step S1, using vertical liquid phase epitaxy technology on the top of the substrate to form an epitaxial growth layer; Step S2, performing interdiffusion annealing treatment on the whole material to generate a longitudinally distributed composition gradient layer in the epitaxial growth layer; Step S3, doping the composition gradient layer to form the P absorption layer; For the composition gradient layer, doping is carried out by the method of gold doping or annealing to form the hole-doped P absorption layer; Step S4, from the top layer of the epitaxial growth layer, dry etching is used to etch the first groove and the second groove from top to bottom, and the depth penetrates the epitaxial growth layer to reach the top of the substrate; the first groove forms an ion implantation hole corresponding to the N electrode; the second groove forms a common electrode hole corresponding to the P electrode; Step S5, in the ion implantation hole, ion implantation is carried out to form the laterally distributed N contact layer; Step S6, performing annealing and junction-pushing treatment on the whole material, so as to form an N multiplication layer laterally outside the N contact layer; the N multiplication layer contacts the P absorption layer; Step S7, metal deposition is carried out in the ion implantation hole and the common electrode hole; Then the N electrode is formed on the ion implantation hole where the metal deposition is completed, and the P electrode is formed on the common electrode hole where the metal deposition is completed.

6. The preparation method of the dumping type linear single-photon avalanche detector according to claim 5, characterized in that, In step S1, the epitaxial growth layer includes mercury cadmium telluride material in contact with the substrate at the lower layer and cadmium telluride material on the surface.

7. The preparation method of the tilting linear single-photon avalanche detector according to claim 5, wherein In step S2, the temperature of the interdiffusion annealing treatment is 300 to 500 degrees Celsius, and the annealing time is 1 to 48 hours.

8. The preparation method of the tilting linear single-photon avalanche detector according to claim 5, characterized in that, In step S4, the power of the inductively coupled plasma for the dry etching is 500 to 1500 watts, the radio frequency power is 10 to 50 watts, the argon gas flow rate is less than or equal to 20 standard milliliters per minute, the hydrogen gas flow rate is less than or equal to 25 standard milliliters per minute, the methane gas flow rate is less than or equal to 25 standard milliliters per minute, and the time is 1 to 120 minutes.

9. The preparation method of the tilting linear single-photon avalanche detector according to claim 5, characterized in that In step S5, the size of the ion implantation hole is 5 to 20 microns; boron ion implantation is used for the ion implantation, the energy of the boron ions is 120 to 180 keV, the dose is 1×10 13 to 1×10 15 cm -2 , and the beam current is 50 to 200 μA.

10. The preparation method of the tilting type linear single-photon avalanche detector according to claim 5, characterized in that, In step S6, in the annealing and junction-pushing treatment, the junction-pushing annealing temperature is 150 to 250 degrees Celsius, and the time is 120 to 250 seconds.

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