Tellurium-cadmium-mercury double-color avalanche detector based on vertical liquid phase epitaxial material

Abstract

The utility model discloses a tellurium-cadmium-mercury double-color avalanche detector based on a vertical liquid phase epitaxial material. According to the detector, a P-type medium-wave HgCdTe epitaxial material with component gradient is grown on a CdZnTe substrate through vertical liquid phase epitaxy, an N + type contact layer is formed through ion implantation, and an N-type multiplication layer is formed in an annealing junction pushing mode. According to the invention, a device preparation mode of a photosensitive element with staggered mesa junctions and planar junctions is introduced, so that an absorption region of a mesa junction region is positioned in a component gradient short wave material, and an absorption region of a planar junction region is positioned in a transverse medium wave material, thereby preparing an on-chip integrated two-color wave band response avalanche infrared detector by utilizing a vertical liquid phase epitaxy mode. The preparation difficulty and cost of a bicolor material and a device are reduced, and the size, the weight and the power consumption of a detection system are reduced while wide-spectrum and multi-band active and passive dual-mode detection is realized.

Description

Technical Field

[0001] The present application relates to the field of semiconductor infrared detection technology, and in particular to a mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxial material. Background Art

[0002] Dual-color detectors can obtain target information from two bands at the same time, improving the detection capability of complex environments. Compared with the traditional method of separating different detection bands through optical systems and then detecting on different detector arrays, monolithic integrated dual-color detection does not have the problem of spatial alignment and temporal registration of different arrays, thereby reducing the size, weight and power consumption of the overall detection system.

[0003] HgCdTe dual-color detectors generally have two working modes. The mode in which the working band is selected by bias voltage and only one band signal can be read out at a time is called sequential mode, which is composed of two back-to-back photodiodes connected; the mode in which two bands can be operated at the same time and two band signals can be output at the same time is called simultaneous mode, which is composed of two parallel photodiodes. The device materials of both modes adopt multi-layer heterojunction structure. Major international research institutions and companies have enriched the development of HgCdTe dual-color detectors on different technical routes using molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD) technology. Compared with molecular beam epitaxy and metal organic chemical vapor deposition, liquid phase epitaxy technology is cheaper and easier to operate. Although horizontal liquid phase epitaxy (LPE) technology can grow multi-layer HgCdTe heterojunction materials, it is still inferior to vertical liquid phase epitaxy technology in terms of material size, quality and growth difficulty.

[0004] As a new type of detector developed in the last two decades, HgCdTe infrared avalanche photodiode (APD) array is an important device for weak signal detection and three-dimensional active / passive detection applications due to its advantages of high gain, high sensitivity, high-speed detection and almost no excess noise. PIN-type HgCdTe APD devices based on vertical liquid phase epitaxial materials can be formed into N + -N - -P junction, the process is simple and mature, with good controllability and high yield rate. Summary of the invention

[0005] In order to meet the requirements of size, weight and power consumption of the detection system and reduce the difficulty and cost of preparing dual-color materials and devices, it is very necessary to prepare infrared devices that can be integrated on-chip and have the advantages of dual-color band response and avalanche detection, so as to achieve wide-spectrum, multi-band active and passive dual-mode detection.

[0006] One of the purposes of the present application is to provide a mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxial material, comprising: a substrate (1), on which an absorption layer is grown using vertical liquid phase epitaxial technology, comprising a short-wave p-HgCdTe component gradient layer (2) and a medium-wave p-HgCdTe epitaxial layer (3), and ion implantation forms an n + -HgCdTe contact layer (5), annealing to form n - -HgCdTe multiplication layer (4), a common electrode (6) is located on the medium-wave p-HgCdTe epitaxial layer (3), and a photosensitive element electrode (7) is located on the n + - On the HgCdTe contact layer (5).

[0007] In some embodiments, the substrate (1) material is CdZnTe.

[0008] In some embodiments, the short-wave p-HgCdTe composition gradient layer (2) has a thickness of 1 to 3 μm, and the Cd composition changes gradually from 0.8 (±0.05) to 0.3 (±0.05).

[0009] In some embodiments, the medium-wave p-HgCdTe medium-wave epitaxial layer (3) has a thickness of 3-8 μm, a Cd component of 0.29-0.33, and a P-type concentration of 2×10 15 ~5×10 16 cm -3 .

[0010] In some embodiments, the n - -HgCdTe multiplication layer (4) has a thickness of 3-5 μm, a Cd component of 0.29-0.33, and an N-type concentration of 1×10 13 ~5×10 14 cm -3 .

[0011] In some embodiments, the n + -HgCdTe contact layer (5) has a thickness of 1-2 μm, a Cd component of 0.29-0.33, and an N-type concentration of 1×10 17 ~5×10 17 cm -3 .

[0012] In some embodiments, the common electrode (6) and the photosensitive element electrode (7) are both ohmic electrodes, and the material is any one of Cr, Sn, Ti, Pt, Au, or an alloy of two or more of Cr, Sn, Ti, Pt, Au.

[0013] The second object of the present application is to provide a method for preparing a mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxial material, comprising the following steps:

[0014] A medium-wave HgCdTe epitaxial layer is grown on the substrate (1) using a vertical liquid phase epitaxial material to form a natural p-HgCdTe component gradient layer (2) and a p-HgCdTe medium-wave epitaxial layer (3);

[0015] SiO2 and photoresist are used as masks on the outermost layer of the device, and part of the mesa is left by photolithography and development, and a structure where the mesa junction and the plane junction are adjacent is formed by dry / wet etching, and the p-HgCdTe composition gradient layer (2) is etched;

[0016] Ion implantation is performed on the p-HgCdTe medium wave epitaxial layer (3) to form n + -HgCdTe contact layer (5), annealing to form n - -HgCdTe multiplication layer (4), and finally evaporating the common electrode (6) and the photosensitive element electrode (7) on the photolithography mask pattern;

[0017] This application adopts the above technical method, and its beneficial effects are as follows:

[0018] The medium-wave HgCdTe device material with a natural component gradient layer is grown by vertical liquid phase epitaxy. Compared with molecular beam epitaxy and metal organic chemical vapor deposition, the technology is relatively simple, the material quality is better, and the cost is lower. Compared with horizontal liquid phase epitaxy, the material size that can be grown is larger and the yield is higher. The avalanche device is prepared by using vertical liquid phase epitaxial material to form a photosensitive unit adjacent to the mesa junction and the plane junction, so that the absorption layer in the mesa junction area is a p-HgCdTe component gradient layer (2) that reflects short-wave characteristics, and the absorption layer in the plane junction area is a lateral p-HgCdTe medium-wave epitaxial layer (3) that reflects medium-wave characteristics. The multi-spectral band and wide-spectrum infrared avalanche detector integrated on the chip is finally obtained, which helps to improve the detection and discrimination capabilities of complex signals and weak signals, and is also beneficial to reducing the size, weight, power consumption and cost of the overall detection system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a schematic structural diagram of a mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxial material provided in Example 1 of the present invention.

[0021] Figure 2A flow chart of the steps of a method for preparing a mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxial material provided in Example 2 of the present invention.

[0022] Figure 3 This is the response spectrum of the mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxial material.

[0023] Figure 4 This is a graph showing the variation of avalanche gain with bias voltage for a HgCdTe two-color avalanche detector based on vertical liquid phase epitaxial material. DETAILED DESCRIPTION

[0024] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0025] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0026] Example 1

[0027] See also Figure 1 , which is a schematic structural diagram of a mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxial material provided in Example 1 of the present application, comprising: a substrate (1), a p-HgCdTe composition gradient layer (2) and a medium-wave p-HgCdTe epitaxial layer (3), n + -HgCdTe contact layer (5), n - -HgCdTe multiplication layer (4), common electrode (6), photosensitive element electrode (7).

[0028] In this embodiment, the substrate (1) is made of CdZnTe.

[0029] In this embodiment, the medium-wave p-HgCdTe medium-wave epitaxial layer (3) is a target medium-wave material grown by vertical liquid phase epitaxy, with a thickness of 3-8 μm, a Cd component of 0.29-0.33, and a P-type concentration of 2×10 15 ~5×10 16 cm -3 .

[0030] In this embodiment, the short-wave p-HgCdTe component gradient layer (2) is a transition layer naturally formed during the liquid phase epitaxial growth of the medium-wave epitaxial layer (3), with a thickness of 1 to 3 μm, and the Cd component gradually changes from 0.8 (±0.05) to 0.3 (±0.05).

[0031] In this embodiment, the n+ -HgCdTe contact layer (5) is formed by ion implantation of B ions to bombard HgCdTe to form Hg gap filling, with a thickness of 1-2 μm, a Cd component of 0.29-0.33, and an N-type concentration of 1×10 17 ~5×10 17 cm -3 .

[0032] In this embodiment, the n - -HgCdTe multiplication layer (4) is formed by annealing, has a thickness of 3-5 μm, a Cd component of 0.29-0.33, and an N-type concentration of 1×10 13 ~5×10 14 cm -3 .

[0033] In this embodiment, the common electrode (6) and the photosensitive element electrode (7) are both ohmic electrodes, and the material is any one of Cr, Sn, Ti, Pt, Au, or an alloy of two or more of Cr, Sn, Ti, Pt, Au.

[0034] The present application provides a mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxial material, wherein the photosensitive element is composed of adjacent table junctions and planar junctions, wherein the absorption layer in the table junction region is a p-HgCdTe component gradient layer (2) which exhibits short-wave characteristics, and the absorption layer in the planar junction region is a lateral p-HgCdTe medium-wave epitaxial layer (3) which exhibits medium-wave characteristics. - The high concentration in the region enables the device to have avalanche detection capability, which can realize wide-spectrum weak signal detection in two bands.

[0035] Example 2

[0036] See also Figure 2 , the method for preparing a mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxial material provided in this embodiment 2 comprises the following steps:

[0037] Step S110: growing a medium-wave HgCdTe epitaxial layer on the substrate (1) using a vertical liquid phase epitaxial material to form a natural p-HgCdTe component gradient layer (2) and a p-HgCdTe medium-wave epitaxial layer (3);

[0038] Step S120: using SiO2 and photoresist as masks on the outermost layer of the device, performing photolithography and development to leave part of the mesa, and using dry / wet etching to form a structure where the mesa junction and the plane junction are adjacent, and etching to the p-HgCdTe composition gradient layer (2);

[0039] Specifically, wet etching with photoresist as mask can be used to etch away the area outside the photoresist pattern, or dry etching with SiO2 as mask can be used to first photoetch the SiO2 mask outside the mesa pattern, then dry-etch the mesa, and finally etch away the SiO2.

[0040] Furthermore, the photoresist used is AZ4330, the baking temperature is less than 90° C., and the baking time is greater than 30 min.

[0041] Step S130: ion implantation is performed on the p-HgCdTe medium-wave epitaxial layer (3) to form n + -HgCdTe contact layer (5), annealing to form n - -HgCdTe multiplication layer (4), and finally evaporating the common electrode (6) and the photosensitive element electrode (7) on the photolithography mask pattern;

[0042] Specifically, the ion implantation barrier layer is ZnS, and the ion implantation material B ions have an energy of 100-300 KeV and a dose of 1×10 14 ~1×10 16 cm -2 The electrode evaporation method is electron beam evaporation, thermal evaporation or dual ion beam sputtering coating.

[0043] The method for preparing a mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxial material provided in the present application does not require the use of a complex and expensive method to grow multi-layer device materials and in-situ doping processes, and there is no interface area with component mismatch and obvious defect dislocation. It is only necessary to design a photolithography pattern on the nearly single-layer device body material grown by vertical liquid phase epitaxy, first partially etch the table, and then anneal and push the junction after ion implantation to form an on-chip integrated device in which the planar junction APD and the table junction APD are interlaced. The absorption layer in the table junction area is a p-HgCdTe component gradient layer (2), which reflects the characteristics of a short-wave avalanche detector, and the absorption layer in the planar junction area is a lateral p-HgCdTe medium-wave epitaxial layer (3), which reflects the characteristics of a medium-wave avalanche detector, thereby realizing wide-spectrum and weak signal detection in two bands.

[0044] It can be understood that the technical features of the above-described embodiments can be arbitrarily combined. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0045] The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted as limiting the scope of protection of the present application in any way. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with the technicians in this field without creative work, should be included in the scope of protection of the present application.

Claims

1. A mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxial material, characterized in that: The detector comprises: a substrate (1), on which an absorption layer is grown using vertical liquid phase epitaxial technology, comprising a short-wave p-HgCdTe component gradient layer (2) and a medium-wave p-HgCdTe epitaxial layer (3), and ion implantation forms an n + -HgCdTe contact layer (5), annealing to form n - -HgCdTe multiplication layer (4), a common electrode (6) is located on the medium-wave p-HgCdTe epitaxial layer (3), and a photosensitive element electrode (7) is located on the n + -HgCdTe contact layer (5).

2. The mercury cadmium telluride two-color avalanche detector based on vertical liquid phase epitaxy material according to claim 1, characterized in that: The substrate is CdZnTe.

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