HgCdTe photodiode structure utilizing resonant cavity for absorption
By optimizing the ring hole structure and resonant cavity absorption technology, the problems of reducing luminous flux and difficult process implementation in DRS company's HDVIP structure are solved, and high light absorption and process simplification are achieved, which are suitable for the field of hyperspectral detection.
Patent Information
- Application Number
- CN202421023969.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-13
- Publication Date
- 2025-03-11
- Estimated Expiration
- 2034-05-13
AI Technical Summary
In the prior art, DRS's HDVIP structure has problems of reducing luminous flux and difficulty in implementing process during the preparation process, especially in the thickness of the mercury cadmium tellurium layer and the depth-to-width ratio of the long-wave device.
By optimizing the ring hole structure, a resonant cavity absorbed mercury cadmium tellurium photodiode structure is adopted, including an insulating material, a CdTe layer, a mercury tellurium layer, a buried common electrode and a metal reflective layer, the thickness of each layer of the material is adjusted to achieve high light absorption in a specific wavelength region and reduce the difficulty of process preparation.
The light absorption of more than 95% in a specific wavelength region is achieved, the thickness requirements of the mercury cadmium tellurium layer are reduced, the etching process is simplified, the light incident flux and common electrode area are increased, the voltage uniformity is improved, and the application value in the field of hyperspectral detection is achieved.
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Figure CN222602918U_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of infrared and optoelectronics, and in particular relates to a mercury cadmium telluride photodiode structure utilizing resonant cavity absorption. Technical Background
[0002] Loop-hole photodiode is a structure that is directly connected to the readout circuit (ROIC) below by etching a via hole in the center of p-type HgCdTe and growing a metal layer by sputtering, evaporation, etc. The HDVIP (High Density Vertical Intergreted Photodiode) focal plane device of DRS Company in the United States adopts this structure.
[0003] However, the preparation of DRS's HDVIP structure has the following difficulties:
[0004] Placing the p-region common electrode on the upper surface of the pixel will reduce the incident light flux. The HgCdTe thickness of the long-wave device needs to reach 6μm, and the HgCdTe thickness of the medium-wave device needs to reach 4μm to achieve a higher photocurrent. This thickness of HgCdTe requires a large depth-to-width ratio for the through-hole etching process. For long-wave HgCdTe devices with a center distance of 6μm, the through-hole diameter is generally 2μm, and the through-hole depth needs to be greater than 6μm, making the process difficult to implement. Summary of the invention
[0005] In order to overcome the shortcomings of the prior art, the present invention provides a mercury cadmium telluride photodiode structure using resonant cavity absorption, and reduces the difficulty of process preparation by optimizing the ring hole structure.
[0006] The purpose of the present invention is achieved by the following technical solutions:
[0007] The structure includes an insulating material, a CdTe layer, a mercury cadmium telluride layer, a buried common electrode and a metal reflective layer, an epoxy resin, a readout circuit, and a pixel center electrode;
[0008] in,
[0009] The insulating material achieves a coherent perfect absorption condition at a desired specific wavelength by adjusting the thickness;
[0010] The CdTe layer is an inter-diffusion annealed CdTe graded layer on both sides of the mercury cadmium telluride for reducing tunneling current;
[0011] The mercury cadmium telluride layer is a light absorbing material, and photoelectric conversion is formed within the material;
[0012] The buried common electrode and the metal reflective layer are metal layers buried under the mercury cadmium telluride material, and are used for reflection under the common electrode and the mercury cadmium telluride material at the same time;
[0013] The epoxy resin is used to bond the detector and the readout circuit;
[0014] The readout circuit is a silicon integrated circuit for integrating photocurrent and outputting a digital signal;
[0015] The pixel center electrode is a separate electrode for each pixel, used to collect photocurrent and form an interconnection with each pixel electrode on the readout circuit.
[0016] The insulating material is a single-layer ZnS film. When a multi-layer film is used, the material in contact with CdTe is ZnS.
[0017] The buried common electrode and the metal reflective layer are buried under the mercury cadmium telluride material, isolated from the mercury cadmium telluride by insulating materials, and use VIB and IB group metals. The metal layer covers other areas except the through hole position, and the metal layer is isolated from the internal electrode of the through hole.
[0018] Compared with the prior art, the beneficial effects of the present invention are:
[0019] 1 By adjusting the thickness of each material layer using the photonic crystal structure and the effect of coherent perfect absorption, light absorption greater than 95% can be achieved in a specific wavelength region.
[0020] 2 Reducing the MCT thickness reduces the aspect ratio requirements of the etching process, allowing chemical etching to match the device's manufacturing process.
[0021] 3 Compared with the HDVIP structure of DRS, the common electrode is buried inside, which increases the light incident flux on the upper surface. And there is a larger common electrode area, which increases the uniformity of voltage.
[0022] 4 The structure of the present invention is regulated by the materials on both sides of the MCT. For different MCT thicknesses, the maximum absorption at different wavelengths can be achieved by precisely regulating the thickness of ZnS, which has application value in the field of hyperspectral detection. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 Structure diagram of a HgCdTe photodiode using resonant cavity absorption.
[0024] In the figure: 1 is an insulating material, 2 is a CdTe layer, 3 is a mercury cadmium telluride layer, 4 is a buried common electrode and a metal reflective layer, 5 is an epoxy resin, 6 is a readout circuit, and 7 is a pixel center electrode. DETAILED DESCRIPTION
[0025] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.
[0026] Example 1
[0027] The present invention provides a solution suitable for MCT (ie, mercury cadmium telluride layer 3) with a pixel center distance of 6 μm, a component of 0.23 and a thickness of 1.5 μm, which can achieve an absorption of more than 95% at 9.4 μm.
[0028] like Figure 1 As shown, CdTe passivation is performed on both sides of the MCT material (i.e., forming a CdTe layer 2, or a CdTe gradual change layer), the thickness of the CdTe layer 2 is 300nm, and a ZnS layer (i.e., insulating material 1) is grown on the CdTe layer 2 on both sides. The insulating material 1 on both sides is used to match the thickness condition for achieving coherent perfect absorption of a specific wavelength. When the thickness of the insulating material 1 on both sides is 100nm, more than 95% absorption can be achieved at a wavelength of 9.4μm. The metal layer used for reflection, that is, the metal layer that also serves as a common electrode, has a thickness of 200nm, and the greater the thickness, the better the voltage uniformity as a common electrode. The epoxy resin 5 of the lower layer can use DW-3 low-temperature glue. The diameter of the through hole is 2μm, which can be made smaller under the condition of higher process precision, and the duty cycle can be further improved. The thickness of the metal layer on the side wall of the through hole is about 200nm.
[0029] For other bands that need to achieve coherent perfect absorption, ZnS is replaced with other materials based on this structure, or several materials are stacked, and the structures of these materials are changed to form photonic crystals or metasurfaces.
[0030] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.
Claims
1. A mercury cadmium telluride photodiode structure using resonant cavity absorption, characterized in that: The structure includes an insulating material, a CdTe layer, a mercury cadmium telluride layer, a buried common electrode and a metal reflective layer, an epoxy resin, a readout circuit, and a pixel center electrode; in, The insulating material achieves a coherent perfect absorption condition at a desired specific wavelength by adjusting the thickness; The CdTe layer is an inter-diffusion annealed CdTe graded layer on both sides of the mercury cadmium telluride for reducing tunneling current; The mercury cadmium telluride layer is a light absorbing material, and photoelectric conversion is formed within the material; The buried common electrode and the metal reflective layer are metal layers buried under the mercury cadmium telluride material, and are used for reflection under the common electrode and the mercury cadmium telluride material to form a resonant cavity structure; The epoxy resin is used to bond the detector and the readout circuit; The readout circuit is a silicon integrated circuit for integrating photocurrent and outputting a digital signal; The pixel center electrode is a separate electrode for each pixel, used to collect photocurrent and form an interconnection with each pixel electrode on the readout circuit.
2. The mercury cadmium telluride photodiode structure using resonant cavity absorption according to claim 1, characterized in that: The insulating material is a single-layer ZnS film. When a multi-layer film is used, the material in contact with CdTe is ZnS.
3. The mercury cadmium telluride photodiode structure using resonant cavity absorption according to claim 1, characterized in that: The buried common electrode and the metal reflective layer are buried under the mercury cadmium telluride material, isolated from the mercury cadmium telluride by insulating materials, and use VIB and IB group metals. The metal layer covers other areas except the through hole position, and the metal layer is isolated from the internal electrode of the through hole.