A mercury cadmium telluride detector chip with a high saturation threshold and a preparation method thereof

Abstract

The present invention discloses a mercury cadmium telluride detector chip with a high saturation threshold and a preparation method thereof. The mercury cadmium telluride detector chip includes a substrate, an epoxy resin adhesive, a p-type photosensitive layer, an n-type ion implantation layer, a passivation layer, an n-type electrode layer, and a p-type electrode layer. The p-type photosensitive layer is a Hg 1‑ x Cd x Te component gradient layer, which sequentially includes a Cd component linearly gradient Hg 1‑x Cd x Te layer and a Cd component non-linearly gradient Hg 1‑x Cd x Te layer. The Cd component x gradually changes from high to low from the upper surface of the Cd component non-linearly gradient Hg 1‑x Cd x Te layer to the lower surface of the Cd component linearly gradient Hg 1‑x Cd x Te layer. The n-type ion implantation layer of the chip of the present invention is formed in the Cd component non-linearly gradient Hg 1‑x Cd x Te layer. The strong built-in electric field introduced by the gradient bandgap improves the drift velocity of holes, reduces the accumulation of holes in the space charge region, simultaneously inhibits the diffusion motion of carriers in the p region, reduces the collection efficiency of pn junctions for photo-generated electrons in the p region, reduces the carrier concentration in the space charge region, increases the saturation threshold of the chip, and enables operation at room temperature with zero bias voltage.

Description

Technical Field

[0001] The present invention relates to a photodetector for mid-infrared laser power measurement, and particularly to a mercury cadmium telluride detector chip with a high saturation threshold and a preparation method thereof. Background Art

[0002] When mid-infrared lasers propagate in the atmosphere, they have a very high transmittance and can achieve efficient long-distance energy transmission. Therefore, they have broad application prospects in the fields of optoelectronic countermeasures, target recognition and detection, atmospheric environment monitoring, and spectral monitoring and analysis. With the gradual in-depth application of mid-infrared lasers in various fields, the demand for power meters for mid-infrared lasers is increasing day by day. At present, most of the laser power meters developed in China are mainly single-channel products with a wavelength range within 400nm to 1650nm. They are inferior to foreign power meters in terms of performance indicators, functional diversity, technical level, working reliability, and ease of use. Especially for high-end power meter products for mid-infrared laser measurement, they are basically monopolized by foreign companies.

[0003] Photovoltaic power probes are generally used in weak laser power measurement because they are prone to saturation under strong light radiation. When a high-power incident light irradiates a photodetector, when the concentration of non-equilibrium minority carriers generated by the incident light approaches or exceeds the concentration of majority carriers in the original equilibrium state, the concentration of photo-generated carriers in the space charge region is very high. Since the mobility of holes is lower than that of electrons, a large number of holes remaining in the space charge region generate a space charge effect, reducing the built-in electric field of the pn junction, causing the pn junction to reach the separation limit of electron-hole pairs, and the output current to saturate. Therefore, to increase the saturation threshold of the detector under large injection, it is necessary to weaken the space charge effect and reduce the interference of photo-generated carriers on the pn junction electric field.

[0004] Many domestic and foreign literatures have reported using the built-in electric field generated by the composition gradient to affect the movement and distribution of carriers. In the chip structure design of mercury cadmium telluride detectors, this built-in electric field is often used to accelerate the movement of photo-generated minority carriers towards the pn junction, and by increasing the minority carrier diffusion length and suppressing interface or surface recombination, the detection performance of mercury cadmium telluride detectors is improved. However, when working under high-power light incidence, this chip structure is more prone to saturation.

[0005] CN111554761B discloses a detector chip, including a mercury cadmium telluride thin film and a chip structure. The chip structure includes a pn junction, a readout circuit, and indium pillars. Among them, the pn junction is formed on the back surface of the mercury cadmium telluride thin film, and the back surface of the mercury cadmium telluride thin film is the epitaxial starting interface during the epitaxial growth of the mercury cadmium telluride thin film. The readout circuit is located on the back side of the mercury cadmium telluride thin film and is connected to the pn junction through the indium pillars. In this invention, by forming a junction on the back surface of the mercury cadmium telluride thin film, the pn junction is formed in the high-composition material region on the back surface of the mercury cadmium telluride thin film (i.e., at the epitaxial interface), reducing the leakage current of the detector chip and enhancing the chip response signal, thereby significantly improving the working performance of the detector. The chip of this invention adopts a back-illuminated structure, where the incident light points from the low-Cd composition region to the high-Cd composition region. A large number of photo-generated carriers are generated in the low-Cd composition region of the mercury cadmium telluride thin film, while the pn junction is formed in the high-composition material region on the back surface of the mercury cadmium telluride thin film (i.e., at the epitaxial interface). The photo-generated carriers are collected by the pn junction below the absorption region through diffusion motion. The pn junction of this chip structure is in the built-in electric field generated by the composition gradient, which points from the high-Cd composition to the low-Cd composition. The electric field force on the photo-generated minority carriers in the absorption region is opposite to the direction of their diffusion to the space charge region. However, the response signal of the chip of this invention is enhanced, indicating that the chip structure of this invention does not effectively suppress the diffusion of photo-generated minority carriers to the space charge region, and thus cannot reduce the interference of photo-generated carriers on the pn junction electric field under large injection.

[0006] To increase the saturation threshold of the detector, the detector is often operated under a reverse bias voltage to enhance the built-in electric field in the space charge region of the pn junction. However, a large bias voltage will increase the dark current and Joule heat. When the Joule heat is large enough, the detector will experience thermal failure. Summary of the Invention

[0007] Aiming at the problems that traditional mercury cadmium telluride detector chips are prone to saturation under high-power light incidence and have a low saturation threshold, etc., the present invention provides a mercury cadmium telluride detector chip with a high saturation threshold that can operate at room temperature with zero bias voltage and reduce the space charge effect under high-power light incidence, as well as a preparation method thereof.

[0008] The technical solution of the present invention is as follows:

[0009] A mercury cadmium telluride detector chip with a high saturation threshold, including a substrate 1, an epoxy resin adhesive 2, a p-type photosensitive layer 3, an n-type ion implantation layer 4, a passivation layer 5, an n-type electrode layer 6, and a p-type electrode layer 7, where:

[0010] The p-type photosensitive layer 3 is a Hg 1-x Cd x Te composition gradient layer, which sequentially includes a Cd composition linearly gradient Hg 1-x Cd x Te layer 31 and a Cd composition non-linearly gradient Hg1-x Cd x The CdTe layer 32, the Cd component x gradually changes non-linearly from high to low to Hg with the Cd component 1-x Cd x The upper surface of the Te layer 32 gradually changes to the Hg with the linearly changing Cd component 1-x Cd x The lower surface of the Te layer 31;

[0011] The Hg with the non-linearly changing Cd component 1-x Cd x The x value range of the CdTe layer 32 satisfies b ≤ x ≤ a, a > b, the maximum value of a is 0.8, the minimum value is 0.5, the maximum value of b is 0.36, the minimum value is 0.25, and the thickness is 2 - 4 μm;

[0012] The n-type ion implantation layer 4 is formed in the Hg with the non-linearly changing Cd component 1-x Cd x In the CdTe layer 32, the top surface of the n-type ion implantation layer 4 and the Hg with the non-linearly changing Cd component 1-x Cd x The top surface of the Te layer 32 is flush, and the thickness of the n-type ion implantation layer 4 is 1 - 1.8 μm;

[0013] The Hg with the linearly changing Cd component 1-x Cd x The lower surface of the CdTe layer 31 is bonded to the substrate (1) by epoxy resin glue (2).

[0014] Preferably, the Hg with the linearly changing Cd component 1-x Cd x The CdTe layer 31 and the Hg with the non-linearly changing Cd component 1-x Cd x The p-type doping concentration of the Te layer 32 at room temperature is 1×10 17 cm －3～ 5×10 18 cm －3 .

[0015] Preferably, the passivation layer 5 is zinc sulfide.

[0016] Preferably, the n-type electrode layer 6 is In / Au.

[0017] Preferably, the p-type electrode layer 7 is Sn / Au.

[0018] Preferably, the substrate 1 is sapphire, silicon or silicon carbide.

[0019] Correspondingly, the present invention also discloses a preparation method of a mercury cadmium telluride detector chip with a high saturation threshold, including:

[0020] S1. Provide a mercury cadmium telluride thin film epitaxially grown on cadmium zinc telluride, and fit the infrared transmission spectrum of the epitaxial mercury cadmium telluride thin film through a multi-layer model and a film system transfer matrix to obtain the longitudinal component distribution of the Cd component in the mercury cadmium telluride thin film along the growth direction;

[0021] S2. Provide a substrate;

[0022] S3. Bond the mercury cadmium telluride thin film epitaxially grown on cadmium zinc telluride to the substrate with epoxy resin glue;

[0023] S4. Remove cadmium zinc telluride by rough polishing, fine polishing and cadmium zinc telluride etching solution, and then etch the interface with Br-HBr etching solution to expose the surface;

[0024] S5. Form an n-type ion implantation layer by boron ion implantation;

[0025] S6. Prepare a passivation layer by thermal evaporation technology;

[0026] S7. Prepare an n-type electrode layer by ion beam sputtering;

[0027] S8. Prepare a p-type electrode layer by ion beam sputtering.

[0028] Compared with the traditional mercury cadmium telluride detector chip, the advantages of the present invention are as follows:

[0029] 1. Reduce the space charge effect and increase the saturation threshold.

[0030] (1) Increase the drift velocity of holes in the space charge region

[0031] In the Cd component non-linearly graded Hg 1-x Cd x Te layer of the n-type ion implantation layer of the present invention, the strong built-in electric field introduced by the graded bandgap accelerates the drift motion of holes, and reduces the accumulation of holes in the space charge region under high-power light incidence.

[0032] (2) Reduce the carrier concentration in the space charge region

[0033] The thickness of the n-type ion implantation layer of the present invention is less than that of the Cd component non-linearly graded Hg 1-x Cd x Te layer. The strong built-in electric field introduced by the graded bandgap inhibits the diffusion motion of carriers in the p region to the space charge region, reduces the collection efficiency of minority carriers generated by light in the p region by the pn junction, and reduces the carrier concentration in the space charge region.

[0034] 2. It can operate at room temperature with zero bias voltage. Description of the Drawings

[0035] Figure 1Schematic diagram of the HgCdTe detector chip with a high saturation threshold of the present invention.

[0036] Figure 2 Schematic diagram of the energy band variation of the Hg1-xCdxTe composition gradient layer of the present invention.

[0037] Figure 3 Cd composition distribution diagram of the Cd composition non-linearly graded Hg1-xCdxTe layer in Example 1.

[0038] Figure 4 Cd composition distribution diagram of the Cd composition non-linearly graded Hg1-xCdxTe layer in Example 2.

[0039] Figure 5 Cd composition distribution diagram of the Cd composition non-linearly graded Hg1-xCdxTe layer in Example 3.

[0040] Figure 6 Optical responses of the comparative example and Example 3 under laser irradiation at room temperature. Detailed implementation manners

[0041] Next, the technical solutions in the embodiments of the present invention will be described in detail with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] Traditional HgCdTe detector chips generally aim to detect weak signals. In the design, quantum efficiency is concerned, and the collection efficiency of photo-generated carriers is improved. When the device is irradiated by high-power light, it is easy to saturate. In order to increase the saturation threshold of the HgCdTe detector chip, the present invention forms an n-type ion implantation layer in the Cd composition non-linearly graded Hg 1-x Cd x Te layer, and the thickness of the n-type ion implantation layer is less than that of the Cd composition non-linearly graded Hg 1-x Cd x Te layer. The strong built-in electric field introduced by the graded bandgap increases the drift velocity of holes, reduces the accumulation of holes in the space charge region. At the same time, this electric field inhibits the diffusion movement of carriers in the p region to the space charge region, reduces the collection efficiency of minority photo-generated carriers in the p region by the pn junction, reduces the carrier concentration in the space charge region, increases the saturation threshold of the chip, and realizes operation at room temperature with zero bias voltage.

[0043] Such as Figure 1As shown, the mercury cadmium telluride detector chip with a high saturation threshold of the present invention includes a substrate 1, an epoxy resin adhesive 2, a p-type photosensitive layer 3, an n-type ion implantation layer 4, a passivation layer 5, an n-type electrode layer 6, and a p-type electrode layer 7. Among them, the p-type photosensitive layer 3 is a Hg 1- x Cd x Te composition gradient layer, which sequentially includes a Cd composition linearly gradient Hg 1-x Cd x Te layer 31 and a Cd composition non-linearly gradient Hg 1-x Cd x Te layer 32. The Cd composition x gradually changes from high to low from the upper surface of the Cd composition non-linearly gradient Hg 1-x Cd x Te layer 32 to the lower surface of the Cd composition linearly gradient Hg 1-x Cd x Te layer 31.

[0044] Hg 1-x Cd x In the Hg

[0045] Cd V Te composition gradient layer, a gradient bandgap is caused by the distribution of the Cd composition. The offset of the energy gap edge at 300K can be expressed as:

[0046] ΔE C = 0.45×(1 - x)(eV)

[0047] where ΔE v is the upward offset of the valence band top E v , and ΔE c is the downward offset of the conduction band bottom E c .

[0048] Therefore, there is a built-in electric field formed by the gradient bandgap in the p-type photosensitive layer. The built-in electric field generates an electric field force in the same direction on electrons and holes, and its direction is along the incident light direction from high Cd composition to low Cd composition, that is, from the device surface to the substrate. Figure 2 is a schematic diagram of the energy band change of the Hg 1-x Cd x Te composition gradient layer of the present invention. The Hg 1-x Cd x Te composition gradient layer is grown on cadmium zinc telluride by liquid-phase or vapor-phase epitaxy technology to grow a p-type mercury cadmium telluride thin film, and then obtained by removing cadmium zinc telluride. The high-temperature epitaxy technology enables the Hg 1-x Cd x Te composition gradient layer to include a Cd composition linearly gradient Hg 1-x Cd xHgTe layer with non - linear gradient of Cd component 1-x Cd x Te layer, where the Cd component has a non - linear gradient in Hg 1-x Cd x Due to the non - linear distribution of the Cd component in the HgTe layer, the built - in electric field formed by the graded bandgap is relatively strong.

[0049] In the present invention, the Cd component has a non - linear gradient in Hg 1-x Cd x For the HgTe layer 32, the value range of x satisfies b ≤ x ≤ a, where a > b, the maximum value of a is 0.8, the minimum value is 0.5, the maximum value of b is 0.36, the minimum value is 0.25, and the thickness is 2 - 4 μm. The n - type ion - implanted layer 4 is formed in the HgTe layer with non - linear gradient of Cd component 1-x Cd x In the Te layer 32, the top surface of the n - type ion - implanted layer 4 is flush with the top surface of the HgTe layer with non - linear gradient of Cd component 1-x Cd x Te layer 32, and the thickness of the n - type ion - implanted layer 4 is 1 - 1.8 μm. There is a poor lattice match at the interface between the cadmium zinc telluride and mercury cadmium telluride thin films. In the present invention, Br - HBr etching is used to move the ion - implanted region away from the interface and retain the Cd - component non - linear variable layer that can provide a relatively strong built - in electric field. The n - type ion - implanted layer is formed in the HgTe layer with non - linear gradient of Cd component 1-x Cd x Te layer, and the thickness of the n - type ion - implanted layer is less than that of the HgTe layer with non - linear gradient of Cd component 1-x Cd x Te layer. The relatively strong built - in electric field promotes the drift of electrons and holes towards the substrate direction, affecting the movement and distribution of carriers near the space - charge region. In the space - charge region, this electric - field force increases the drift velocity of holes, reduces the accumulation of holes in the space - charge region, and at the same time inhibits the diffusion movement of carriers in the p - region below the space - charge region, resulting in a low efficiency of photo - generated electrons injected into the space - charge region, reducing the carrier concentration in the space - charge region, increasing the chip saturation threshold, and enabling operation at room - temperature zero - bias voltage.

[0050] In the present invention, the Cd component has a linear gradient in Hg 1-x Cd x The lower surface of the HgTe layer 31 is bonded to the substrate 1 by epoxy resin adhesive 2. The chip has a normal - incidence structure. Since the graded component affects the minority - carrier diffusion length, the normal - incidence structure can ensure that the photo - generated holes generated in the n - type ion - implanted layer are fully collected, promoting the drift of holes towards the p - region, improving the collection efficiency of photo - generated holes in the n - region, and at the same time reducing the collection efficiency of photo - generated electrons in the p - region below the space - charge region.

[0051] The preparation method of the mercury cadmium telluride detector chip with a high saturation threshold of the present invention will be further described in detail below in conjunction with embodiments:

[0052] Use liquid-phase or vapor-phase epitaxy technology to grow p-type mercury cadmium telluride thin films with different x values on cadmium zinc telluride. Fit the infrared transmission spectrum of the epitaxial mercury cadmium telluride thin film material using a multi-layer model and a film system transfer matrix to obtain the component distribution of the Cd component in the mercury cadmium telluride thin film along the growth direction. The calculation formula is:

[0053]

[0054] In the formula: x(z) is the component at a distance z from the substrate interface; xs, d, S, and Δz are the surface component, thickness, component gradient, and diffusion zone width of the epitaxial layer respectively, and erf is the error function.

[0055] In order to obtain a Cd component non-linearly graded Hg 1-x Cd x Te layer, it is necessary to paste the low-Cd component surface of the epitaxially grown p-type mercury cadmium telluride thin film to the substrate with epoxy resin glue, remove cadmium zinc telluride to the interface through rough polishing, fine polishing, and cadmium zinc telluride etching solution, and use Br-HBr etching solution to etch to expose the surface, that is, the upper surface of the Cd component non-linearly graded Hg 1-x Cd x Te layer. The etching time refers to the component distribution of the Cd component in the mercury cadmium telluride thin film along the growth direction obtained.

[0056] Example 1:

[0057] Use vapor-phase epitaxy technology to grow a p-type mercury cadmium telluride thin film on cadmium zinc telluride. The Au doping concentration at room temperature is 5×10 18 cm -3 . Calculate the material component x to be 0.21 through infrared transmission spectrum, and use a multi-layer model and a film system transfer matrix to fit the infrared transmission spectrum to obtain the component distribution of the Cd component in the mercury cadmium telluride thin film along the growth direction. Paste the p-type mercury cadmium telluride thin film to a sapphire substrate, remove cadmium zinc telluride to the interface through rough polishing, fine polishing, and cadmium zinc telluride etching solution, and use 0.5% Br-HBr etching solution to etch the interface for 10 s to expose the upper surface of the Cd component non-linearly graded Hg 1-x Cd x Te layer. The change range of the x value of the Cd component non-linearly graded Hg 1- x Cd x Te layer is 0.25≤x≤0.8, the thickness is 4 μm, and the Cd component change distribution is shown in Figure 3 . The built-in electric field generated by the non-linear change of the Cd component can reach up to 6322 V / cm.

[0058] In the Cd component non-linearly graded Hg1-x Cd x An n-type ion implantation layer is prepared by boron ion implantation on the Te layer. The boron ion implantation energy is 350 keV, and the implantation dose is 1×10 15 cm -2 , forming an n-type ion implantation layer with a thickness of 1.8 μm.

[0059] A passivation layer is prepared by thermally evaporating zinc sulfide, with a thickness of An n-type electrode layer In / Au is prepared on the n-type ion implantation layer by ion beam sputtering, with thicknesses of and An p-type electrode layer Sn / Au is prepared on the Cd-component non-linearly graded Hg 1-x Cd x Te layer by ion beam sputtering, with thicknesses of and

[0060] Example 2:

[0061] A p-type HgCdTe thin film is grown on cadmium zinc telluride by vapor phase epitaxy. The Hg vacancy doping concentration at room temperature is 5×10 17 cm -3 , and the material composition x is calculated to be 0.33 through infrared transmission spectroscopy. The infrared transmission spectrum is fitted using a multi-layer model and the film system transfer matrix to obtain the component distribution of the Cd component in the HgCdTe thin film along the growth direction. The p-type HgCdTe thin film is attached to a silicon substrate, and the cadmium zinc telluride is removed to the interface through rough polishing, fine polishing, and cadmium zinc telluride etching solution. The interface is etched with 0.5% Br-HBr etching solution for 15 s to expose the upper surface of the Cd-component non-linearly graded Hg 1-x Cd x Te layer. The variation range of the x value of the Cd-component non-linearly graded Hg 1-x Cd x Te layer is 0.35 ≤ x ≤ 0.65, with a thickness of 3.1 μm. The Cd component variation distribution is shown in Figure 4 , and the built-in electric field generated by the non-linear change of the Cd component can reach up to 4621 V / cm.

[0062] An n-type ion implantation layer is prepared by boron ion implantation on the Cd-component non-linearly graded Hg 1-x Cd x Te layer. The boron ion implantation energy is 200 keV, and the implantation dose is 5×10 14 cm -2 , forming an n-type ion implantation layer with a thickness of 1.5 μm.

[0063] A passivation layer is prepared by thermally evaporating zinc sulfide, with a thickness of An n-type electrode layer In / Au with thicknesses of and is prepared on the n-type ion implantation layer by ion beam sputtering. 1-x Cd x A p-type electrode layer Sn / Au with thicknesses of and

[0064] Example 3:

[0065] A p-type HgCdTe thin film is grown on CdZnTe by vapor phase epitaxy. The Hg vacancy doping concentration at room temperature is 1×10 17 cm -3 . The material composition x is calculated to be 0.31 through infrared transmission spectroscopy, and the infrared transmission spectrum is fitted using a multi-layer model and the film system transfer matrix to obtain the component distribution of the Cd component in the HgCdTe thin film along the growth direction. The p-type HgCdTe thin film is attached to a silicon carbide substrate. The CdZnTe is removed to the interface through rough polishing, fine polishing, and a CdZnTe etching solution. The interface is etched with a 0.5% Br-HBr etching solution for 20 s to expose the upper surface of the Cd composition non-linearly graded Hg 1-x Cd x Te layer. The variation range of the x value of the Cd composition non-linearly graded Hg 1- x Cd x Te layer is 0.36 ≤ x ≤ 0.5, and the thickness is 2 μm. The Cd component variation distribution is shown in Figure 5 . The built-in electric field generated by the non-linear change of the Cd component can reach up to 3281 V / cm.

[0066] An n-type ion implantation layer is prepared on the Cd composition non-linearly graded Hg 1-x Cd x Te layer by boron ion implantation. The boron ion implantation energy is 100 keV, and the implantation dose is 1×10 14 cm -2 . The thickness of the n-type ion implantation layer is 1 μm.

[0067] A passivation layer is grown by thermal evaporation of zinc sulfide with a thickness of An n-type electrode layer In / Au with thicknesses of and is prepared on the n-type ion implantation layer by ion beam sputtering. 1-x Cd x A p-type electrode layer Sn / Au with thicknesses of and

[0068] Comparative example:

[0069] Adopt the traditional mercury cadmium telluride detector chip structure, directly inject on the low Cd component surface of the epitaxial p-type mercury cadmium telluride thin film to form a pn junction, without the process of removing cadmium zinc telluride, and the material parameters and other preparation processes of the device are the same as those in Example 3.

[0070] Specific implementation effect:

[0071] Figure 6 At 300K, the pulse laser with a wavelength of 3098nm and a pulse width of 200ns is used to irradiate the light response of the comparative example and Example 3. It can be clearly seen that compared with the traditional mercury cadmium telluride detector chip, the mercury cadmium telluride detector chip of the present invention has the characteristic of a high saturation threshold.

[0072] The present invention proposes a mercury cadmium telluride detector chip with a high saturation threshold and a preparation method, effectively solving the problems that the mercury cadmium telluride detector chip is easy to saturate under high-power light incidence and has a low saturation threshold, has high industrial utilization value, and is of great significance to the development of domestic power meters.

Claims

1. A mercury cadmium telluride detector chip with a high saturation threshold, comprising a substrate (1), an epoxy resin adhesive (2), a p-type photosensitive layer (3), an n-type ion implantation layer (4), a passivation layer (5), an n-type electrode layer (6) and a p-type electrode layer (7), characterized in that: The p-type photosensitive layer (3) is a Hg 1-x Cd x Te composition gradient layer, which sequentially includes a Cd composition linearly gradient Hg 1-x Cd x Te layer (31) and a Cd composition non-linearly gradient Hg 1-x Cd x Te layer (32). The Cd composition x gradually changes from high to low from the upper surface of the Cd composition non-linearly gradient Hg 1-x Cd x Te layer (32) to the lower surface of the Cd composition linearly gradient Hg 1-x Cd x Te layer (31); The non-linearly gradually varying Hg of the Cd component 1-x Cd x The value range of x of the Te layer (32) satisfies b ≤ x ≤ a, where a > b, the maximum value of a is 0.8, the minimum value is 0.5, the maximum value of b is 0.36, the minimum value is 0.25, and the thickness is 2 - 4 μm; The n-type ion implantation layer (4) is formed in the Cd-component non-linearly graded Hg 1-x Cd x Te layer (32). The top surface of the n-type ion implantation layer (4) is flush with the top surface of the Cd-component non-linearly graded Hg 1-x Cd x Te layer (32). The thickness of the n-type ion implantation layer (4) is 1 - 1.8 μm; The linearly-graded Hg of the Cd component 1-x Cd x The lower surface of the CdTe layer (31) is bonded to the substrate (1) by an epoxy resin adhesive (2).

2. The mercury cadmium telluride detector chip with a high saturation threshold according to claim 1, wherein: The linearly graded HgCd 1-x Cd x Te layer (31) and the non-linearly graded HgCd 1-x Cd x Te layer (32) have a p-type doping concentration at room temperature of 1×10 17 cm -3 ~5×10 18 cm -3 。 3. The mercury cadmium telluride detector chip with a high saturation threshold according to claim 1, characterized in that: The passivation layer (5) is zinc sulfide.

4. The mercury cadmium telluride detector chip with a high saturation threshold according to claim 1, characterized in that: The n-type electrode layer (6) is In / Au.

5. The mercury cadmium telluride detector chip with a high saturation threshold according to claim 1, characterized in that: The p-type electrode layer (7) is Sn / Au.

6. The mercury cadmium telluride detector chip with a high saturation threshold according to claim 1, characterized in that: The substrate (1) is sapphire, silicon or silicon carbide.

7. A method for preparing a mercury cadmium telluride detector chip with a high saturation threshold as described in claim 1, characterized in that The preparation method comprises the following steps: 1) Provide a mercury cadmium telluride thin film epitaxially grown on cadmium zinc telluride, and fit the infrared transmission spectrum of the epitaxial mercury cadmium telluride thin film through a multi-layer model and a film system transfer matrix to obtain the longitudinal component distribution of the Cd component in the mercury cadmium telluride thin film along the growth direction; 2) Provide a substrate; 3) Bond the mercury cadmium telluride thin film epitaxially grown on cadmium zinc telluride to the substrate through an epoxy resin adhesive; 4) Remove cadmium zinc telluride by rough polishing, fine polishing and cadmium zinc telluride etching solution, and then etch the interface with Br-HBr etching solution to expose the surface; 5) Form an n-type ion implantation layer by boron ion implantation; 6) Prepare a passivation layer by thermal evaporation technology; 7) Prepare an n-type electrode layer by ion beam sputtering; 8) Prepare a p-type electrode layer by ion beam sputtering.

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