An electrically programmable tellurium cadmium mercury wavelength selective detector based on spatial bandgap gradient

Abstract

This invention discloses an electrically programmable mercury cadmium telluride (HgCd) wavelength-selective detector based on a spatial bandgap gradient. The Hg / Cd composition of the absorption layer varies with thickness, allowing the bandgap to be adjusted with depth. Deeper layers have a larger bandgap, absorbing only shorter wavelengths; shallower layers have a smaller bandgap, preferentially absorbing longer infrared wavelengths. By adjusting the applied bias voltage, the positions of the depletion and multiplication regions within the absorption region can be controlled in real time, enabling programmable extraction of photocurrents at different wavelengths within a single-image device. Compared to traditional spectral systems relying on mechanical dispersive or filter arrays, this invention features a compact structure, requires no mechanical components, and offers advantages such as high-speed response and array-based design.

Description

Technical Field

[0001] This invention relates to the field of infrared photoelectric detection technology, and specifically to an electrically programmable mercury cadmium telluride wavelength-selective detector based on spatial bandgap gradient. Background Technology

[0002] Infrared spectroscopy has significant applications in environmental monitoring, gas detection, and biomedical diagnostics. Existing infrared spectroscopy systems typically rely on mechanical gratings or optical filters for spectral dispersion. These solutions are bulky, costly, and difficult to scale up at high speeds, thus failing to meet the demands of portable and real-time systems. Some research has attempted to introduce spectral selection capabilities at the detector chip level, such as integrating micro / nano-structured filters or modulation structures. However, these methods are often limited by optical bandwidth, angle sensitivity, and manufacturing tolerances, making it difficult to simultaneously achieve programmability and high sensitivity.

[0003] Mercury cadmium telluride (Hg) 1-x Cd x Ternary alloys (Te) are used as mid-infrared detection materials, and their bandgap width can be continuously adjusted over a wide range depending on the Hg / Cd composition (x) (typically covering Eg ranges from approximately 0.3 eV to 1.6 eV). Therefore, by setting an Hg / Cd composition gradient along the thickness direction of the device, photons can be selectively absorbed at different depths within the device: regions with smaller band gaps (lower x) absorb long-wave infrared radiation, while regions with larger band gaps (higher x) primarily absorb short-wave infrared radiation. If this is combined with external bias voltage to control the depletion layer position, multi-band response separation of single-image devices can be achieved under different bias voltages. However, traditional HgCd structures (such as planar PIN or SAM structures) exhibit severe intrinsic excitation at high temperatures, leading to excessively high dark current. Furthermore, uncontrolled interband tunneling or high-field-induced tunneling processes in the absorption region must be avoided, otherwise, a sharp increase in dark current will occur. Therefore, how to reduce dark current while achieving a programmable wavelength response is a pressing problem to be solved in current infrared detection technology. Summary of the Invention

[0004] The purpose of this invention is to provide an electrically programmable mercury cadmium telluride wavelength selective detector based on spatial bandgap gradient, which solves the problem of how to achieve programmable wavelength response while reducing dark current in the prior art. By designing the bandgap gradient and controlling the bias voltage, the programmable wavelength selection function is realized, while suppressing dark current and improving operating sensitivity.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An electrically programmable mercury cadmium telluride wavelength selective detector based on spatial bandgap gradient has a substrate on which a mesa structure consisting of a P-type layer, an absorption layer, a buffer layer and an N-type layer are grown sequentially upwards. A passivation layer is wrapped around the mesa structure. A cathode lead is provided in the P-type layer and an anode lead is provided in the N-type layer.

[0007] The band gap of the absorption layer gradually increases and changes in a gradient from the P-type layer toward the buffer layer, so that the main absorption sites of different wavelengths of light are distributed at different depths.

[0008] Between the buffer layer and the N-type layer, a multiplication layer and a control layer are also grown. The multiplication layer grows on top of the buffer layer, and the control layer grows on top of the multiplication layer. The multiplication layer forms a narrow multiplication region inside the detector. The multiplication region is a high electric field region. Within the proposed bias voltage range, the multiplication region can trigger controllable impulse ionization, thereby limiting the required voltage drop within the multiplication region while maintaining high sensitivity. The control layer forms a specific electric field distribution structure with the multiplication layer and the adjacent absorption layer, realizing the precise positioning of the depletion boundary and the multiplication region under the applied bias voltage. The applied bias voltage not only changes the field strength and width of the multiplication region, but also makes the spatial distribution of the multiplication region change in a controlled manner within a certain bias voltage range, thereby realizing the relative fixation of the position of the multiplication region or the controllable adjustment along the depth direction, enabling the bias-programmable acquisition and multiplication of photogenerated carriers at a specific depth.

[0009] The substrate is a zinc cadmium telluride, gallium arsenide, cadmium telluride, or silicon substrate.

[0010] The p-type layer is Hg vacancy-doped p-type mercury cadmium telluride, with a thickness ranging from 0.3 µm to 1 µm, a Cd content of 0.2%, and a doping concentration of [missing information]. .

[0011] The absorption layer is a p-type Hg vacancy-doped Hg. 1-x Cd x Te alloys with thicknesses ranging from 1.7µm to 3µm have Cd content (x) varying along a depth gradient, ranging from 0.20 to 0.35, decreasing with increasing depth. The doping concentration is... .

[0012] The buffer layer is Hg vacancy-doped p-type mercury cadmium telluride, with a thickness ranging from 0.3µm to 0.5µm, a Cd content of 0.40 to 0.43%, and a doping concentration of [missing information]. .

[0013] The multiplication layer is a P-type mercury cadmium telluride doped with Hg vacancy, with a thickness ranging from 0.3µm to 0.5µm, a Cd content of 0.43 to 0.45%, and a doping concentration of [missing value]. .

[0014] The control layer is N-type mercury cadmium telluride, with a thickness ranging from 0.15µm to 0.3µm, a Cd content of 0.43 to 0.45%, and a doping concentration of [missing value]. .

[0015] The N-type layer is N-type mercury cadmium telluride, with a thickness ranging from 0.15µm to 0.3µm, a Cd content of 0.43 to 0.45%, and a doping concentration of [missing information]. .

[0016] The passivation layer is a CdTe and ZnS bilayer passivation film, with CdTe located in the lower layer and ZnS located in the upper layer, and the thickness ratio of CdTe to ZnS is 1:3.

[0017] Both the cathode and anode leads are Cr / Au double-layer electrodes or Sn / Au double-layer electrodes. The ohmic contact layer in contact with the mesa structure is Cr or Sn, and the metal conductive layer is Au. The thickness of Cr or Sn is 0.01μm~0.1μm, and the thickness of Au is 0.1μm~0.6μm. At least two cathode leads are provided.

[0018] In view of the above technical features, the present invention has the following beneficial effects: 1. By designing the bandgap gradient and controlling the bias voltage, a programmable wavelength selection function is achieved, while suppressing dark current and improving operating sensitivity; 2. The bandgap of the absorption layer of the present invention varies with depth and is smaller at the surface, increasing with depth, so that the main absorption positions of different wavelengths of light are distributed at different depths; the above-mentioned synergistic design of the multiplication layer and the control layer enables the device to exhibit obvious wavelength selectivity when scanning bias voltage, thereby realizing a programmable wavelength response for a single pixel; 3. The present invention generates distinguishable spectral responses under different bias voltages, eliminating the need for traditional optical... 4. Due to the increased deep bandgap, the detector design effectively suppresses deep-generation recombination dark currents. Furthermore, by precisely arranging the multiplication region, the high field is concentrated in the controlled region, thereby suppressing uncontrolled tunneling and avalanche processes in the absorption region, reducing the resulting dark current growth, and helping to maintain the detector's response stability in higher temperature ranges. 5. The manufacturing process of this invention is simple and compatible with existing mercury cadmium telluride (MCH) preparation technologies such as in-situ MBE doping. Due to its compact structure and lack of mechanical interference, it is suitable for high-speed, real-time, and arrayed infrared spectroscopy detection. This invention is applicable to portable and arrayed infrared spectroscopy detection systems. Attached Figure Description

[0019] Figure 1 This is a schematic cross-sectional view of the structure of the present invention;

[0020] Figure 2 These are the photocurrent versus voltage graphs for incident light wavelengths of 3-7 micrometers, with the vertical axis representing a logarithmic scale.

[0021] Figure 3 This is a graph showing the relationship between dark current and voltage according to the present invention, with the vertical axis being a logarithmic scale;

[0022] Figure 4 This is a graph showing the relationship between photocurrent and voltage for a detector without a multiplication layer and a control layer, with the vertical axis being a logarithmic scale.

[0023] Figure 5 This is a graph showing the relationship between dark current and voltage for a detector without a multiplication layer or control layer, with the vertical axis being a logarithmic scale.

[0024] Figure 6 yes Figure 3 and Figure 5 The comparison chart.

[0025] In the figure: 1-substrate; 2-P-type layer; 3-absorber layer; 4-buffer layer; 5-multiplication layer; 6-control layer; 7-N-type layer; 8-passivation layer; 9-cathode lead; 10-anode lead. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that some components well-known to those skilled in the art but not related to the main content of the present invention may be omitted in the drawings or description. Additionally, for ease of description, some components in the drawings may be omitted, enlarged, or reduced, but this does not represent the actual size or complete structure of the product.

[0027] An electrically programmable mercury cadmium telluride wavelength-selective detector based on spatial bandgap gradient, such as Figure 1 As shown, it has a substrate 1, which is typically a zinc cadmium telluride, gallium arsenide, cadmium telluride or silicon substrate.

[0028] A mesa structure consisting of a P-type layer 2, an absorption layer 3, a buffer layer 4, and an N-type layer 7 is grown sequentially upward on the substrate 1. A passivation layer 8 is wrapped around the mesa structure. A cathode lead-out terminal 9 is provided in the P-type layer 2, and an anode lead-out terminal 10 is provided in the N-type layer 7.

[0029] Prior to this, the band gap of the absorption layer 3 gradually increases and changes in gradient along the direction of the P-type layer 2 toward the buffer layer 4. The band gap of the absorption layer 3 is smaller at the surface in contact with the P-type layer 2, and increases with depth toward the buffer layer 4, so that the main absorption positions of different wavelengths of light are distributed at different depths.

[0030] Between the buffer layer 4 and the N-type layer 7, a multiplication layer 5 and a regulation layer 6 are also grown. The multiplication layer 5 grows on the buffer layer 4, and the regulation layer 6 grows on the multiplication layer 5.

[0031] The multiplication layer 5 forms a narrow multiplication region inside the detector. The multiplication region is a high electric field region. Within the proposed bias voltage range, the multiplication region can trigger controllable impulse ionization, thereby limiting the required voltage drop within the multiplication region while maintaining high sensitivity. The control layer 6 forms a specific electric field distribution structure with the multiplication layer 5 and the adjacent absorption layer 3 to achieve precise positioning of the depletion boundary and the multiplication region under the applied bias voltage.

[0032] Under the synergistic effect of the pre-designed doping steps and bandgap step structure, the applied bias voltage not only changes the field strength and width of the multiplication region, but also makes the spatial distribution of the multiplication region change in a controlled manner within a certain bias voltage range. This enables the relative fixation of the position of the multiplication region or the controllable adjustment along the depth direction, so that the photogenerated carriers at a specific depth can be collected and multiplied by bias programmable voltage.

[0033] The aforementioned synergistic design of the multiplication layer 5 and the control layer 6 enables the detector to exhibit significant wavelength selectivity when scanning bias, thereby achieving a programmable wavelength response for a single pixel.

[0034] Furthermore, the P-type layer 2 is Hg vacancy-doped P-type mercury cadmium telluride, with a thickness ranging from 0.3µm to 1µm, a Cd content of 0.2%, and a doping concentration of [missing information]. It is used to form a P-type ohmic contact layer.

[0035] The absorption layer 3 is a p-type Hg vacancy-doped Hg. 1-x Cd x Te alloys with thicknesses ranging from 1.7µm to 3µm have Cd content (x) varying along a depth gradient, ranging from 0.20 to 0.35, decreasing with increasing depth. The doping concentration is... .

[0036] The buffer layer 4 is Hg vacancy-doped P-type mercury cadmium telluride, with a thickness ranging from 0.3µm to 0.5µm, a Cd content of 0.40 to 0.43%, and a doping concentration of [missing information]. .

[0037] The material composition and thickness of the buffer layer 4 are designed to increase the thickness between the absorption layer 3 and the multiplication layer 5 in space, thereby delaying the threshold voltage at which the detector undergoes absorption multiplication.

[0038] The multiplication layer 5 is a P-type mercury cadmium telluride doped with Hg vacancy, with a thickness ranging from 0.3µm to 0.5µm, a Cd content of 0.43 to 0.45%, and a doping concentration of [missing value]. .

[0039] The material composition and thickness of the multiplication layer 5 are designed to form a narrow high electric field region (called the multiplication region) inside the detector. The multiplication region can trigger controllable impulse ionization (avalanche amplification) within the proposed bias range, thereby limiting the required voltage drop within the multiplication region while retaining high sensitivity.

[0040] The control layer 6 is N-type mercury cadmium telluride, with a thickness ranging from 0.15µm to 0.3µm, a Cd content of 0.43 to 0.45%, and a doping concentration of [missing information]. .

[0041] The control layer 6 forms a specific electric field distribution structure with the multiplication layer 5 and the adjacent absorption layer 3, thereby achieving precise positioning of the depletion boundary and high field region under the applied bias voltage.

[0042] The depletion boundary refers to the spatial interface between the depletion region and the neutral region. The depletion region is the area where majority carriers are depleted and a fixed space charge density exists, thereby generating an internal electric field. The width and location of the depletion boundary change with the applied bias voltage (especially the reverse bias voltage). For this detector structure, the depletion region is approximated using the following formula.

[0043]

[0044] Where W is the exhaustion width; V is the built-in potential; V is the applied bias voltage. ρ is the dielectric constant of the semiconductor; q is the elementary charge, with a value of 1.602 × 10⁻⁶. -19 Kulun; The doping concentration is the acceptor concentration; here it refers to the doping concentration of P-type mercury cadmium telluride. The acceptor doping concentration is denoted as , here specifically as the doping concentration of N-type mercury cadmium telluride. For the same detector, when the doping concentration ( and Built-in potential Semiconductor dielectric constant Once determined, the depletion width W increases with increasing reverse bias, and the depletion region expands accordingly. The above formula is an idealized approximation of a one-dimensional abrupt junction; in actual heterojunctions, bandgap gradients, or continuously doped profile structures, this formula only provides a qualitative trend.

[0045] In the detector structure of this invention, if a portion of the absorption layer 3 is depleted by the applied bias voltage, the photogenerated carriers generated in that region are rapidly extracted mainly through drift, significantly reducing the recombination probability. If these carriers are guided into the designed high-field multiplication region, controlled impact ionization (avalanche) can occur, achieving gain. This is the fundamental physical mechanism by which the detector achieves programmable bias acquisition and multiplication of photogenerated carriers at a specific depth.

[0046] Under the synergistic effect of the pre-designed doping steps and bandgap step structure, the applied bias voltage not only changes the field strength and width of the high field region, but also makes the spatial distribution of the multiplication region change in a controlled manner within a certain bias voltage range. This enables the relative fixation of the position of the multiplication region or the controllable adjustment along the depth direction, so as to achieve "bias-programmable acquisition or multiplication" of photogenerated carriers at a specific depth (corresponding to a specific cutoff wavelength λc).

[0047] In the detector of this invention, the pre-designed doping ladder and bandgap step structure refer to the spatial engineering design of the doping concentration distribution and Cd composition distribution of mercury cadmium telluride alloy during the epitaxial growth stage, so that the electric field distribution, depletion propagation path and carrier drift behavior exhibit predictable and controlled responses under the action of applied bias voltage.

[0048] The doping steps, by adjusting the space charge density distribution, and the bandgap steps, by adjusting the band barrier height, together determine the spatial distribution of the electric field and the depletion propagation path under reverse bias. The local heterojunction structure formed by the multiplication layer 5 and the control layer 6 causes the voltage to preferentially drop inside the multiplication layer 5, thereby forming a controlled high electric field region within the bias range. As the bias is scanned, the depletion region extends to different depths in the absorption layer 3, allowing photogenerated carriers of different wavelengths absorbed by different component regions to participate in the multiplication process sequentially, thus achieving a bias-programmable wavelength response for a single pixel.

[0049] The N-type layer 7 is N-type mercury cadmium telluride, with a thickness ranging from 0.15µm to 0.3µm, a Cd content of 0.43 to 0.45%, and a doping concentration of [missing information]. It is used to form an N-type ohmic contact layer.

[0050] The passivation layer 8 is a CdTe and ZnS double passivation film, with CdTe located in the lower layer and ZnS located in the upper layer, and the thickness ratio of CdTe to ZnS is 1:3. The passivation layer 8 is used to eliminate dangling bonds and protect the surface of the material, so as to reduce the leakage current on the detector surface and reduce crosstalk.

[0051] Both the cathode lead-out terminal 9 and the anode lead-out terminal 10 are Cr / Au double-layer electrodes or Sn / Au double-layer electrodes. The lower ohmic contact layer that contacts the mesa structure is Cr or Sn, and the upper metal conductive layer is Au. The thickness of Cr or Sn is 0.01μm~0.1μm, and the thickness of Au is 0.1μm~0.6μm.

[0052] At least two cathode leads 9 are provided. Multiple cathode leads 9 prevent uneven electric field distribution within the detector and amplify the absorption of electrons by the anode.

[0053] The following is a specific embodiment of the present invention.

[0054] First, the electrically programmable mercury cadmium telluride wavelength-selective detector based on spatial bandgap gradient of this invention is fabricated. The specific steps are as follows:

[0055] The first step involved using MBE (Metal-Based Electrodeionization) multilayer in-situ doping technology on a cadmium zinc telluride substrate 1. Precise in-situ doping was achieved with a growth thickness of 0.5 µm, a Cd composition of 0.2, and a doping concentration of [missing value]. A P-type mercury cadmium telluride thin film 2; the thickness is 1.7 µm, the Cd content x varies along the depth gradient, ranging from approximately 0.20 to 0.35, decreasing with increasing depth, and the doping concentration is [missing value]. The absorber layer 3 has a thickness of 0.5 µm, a Cd composition of 0.4, and a doping concentration of [missing information]. Buffer layer 4 has a thickness of 0.5µm, a Cd composition of 0.43, and a doping concentration of [missing information]. The multiplication layer 5 has a thickness of 0.3 µm and is doped with a Cd composition of 0.43 and a doping concentration of [missing value]. The control layer 6 has a thickness of 0.3 µm, a Cd composition of 0.43, and a doping concentration of [missing information]. N-type layer 7;

[0056] The second step involves using wet etching technology to form a platform with a depth of approximately 4µm.

[0057] The third step is to grow a CdTe and ZnS bilayer passivation film 8 on the surface of the mesa using magnetron sputtering technology, with CdTe on the bottom and ZnS on the top, and the thicknesses of CdTe and ZnS are 50nm and 150nm, respectively.

[0058] The fourth step is to remove the double-layer passivation film material at the electrode hole location using hydrochloric acid and dichromic acid solutions.

[0059] The fifth step involves growing the cathode lead 9 and the anode lead 10 using ion beam sputtering to form a Sn / Au double-layer electrode, with Sn on the bottom and Au on top, with a thickness of 20nm / 200nm, forming a good gold-semiconductor contact with mercury cadmium telluride.

[0060] like Figure 2 As shown in the figure, the photocurrent of the detector is related to voltage at incident light wavelengths of 3 μm, 4 μm, 5 μm, 6 μm, and 7 μm. As can be seen from the figure, as the applied bias voltage gradually increases, the absorption-amplification channels for different wavelengths are triggered sequentially: the absorption-amplification threshold voltages for 3 μm, 4 μm, 5 μm, 6 μm, and 7 μm are approximately 1.4 volts, 2.2 volts, 3.8 volts, 5.9 volts, and 9.3 volts, respectively. This threshold sequence indicates that this device can achieve multi-band response separation of a single pixel through an applied bias voltage, thus possessing electrically programmable wavelength selection capabilities.

[0061] like Figure 3The figure shows the relationship between the dark current of the detector and voltage. This figure indicates that, within the operating bias range of the device, the overall dark current is below 10. -6 Amperes, while in the operating range corresponding to 3 micrometer, 4 micrometer and 5 micrometer light responses, the dark current drops to about 10. -10 The magnitude is on the order of amperes. The above results demonstrate that the structure of this invention maintains a low dark current level while achieving programmable bias amplification, which is beneficial for improving the device's detection sensitivity and signal-to-noise ratio.

[0062] In contrast, a detector without the multiplication layer 5 and the control layer 6 was fabricated using the same process. The fabrication steps are as follows:

[0063] The first step involved using MBE (Metal-Based Electrodeionization) multilayer in-situ doping technology on a cadmium zinc telluride substrate 1. Precise in-situ doping was achieved with a growth thickness of 0.5 µm, a Cd composition of 0.2, and a doping concentration of [missing value]. A P-type mercury cadmium telluride thin film 2; the thickness is 1.7 µm, the Cd content x varies along the depth gradient, ranging from approximately 0.20 to 0.35, decreasing with increasing depth, and the doping concentration is [missing value]. The absorber layer 3 has a thickness of 0.5 µm, a Cd composition of 0.4, and a doping concentration of [missing information]. Buffer layer 4 has a thickness of 0.3 µm, a Cd composition of 0.43, and a doping concentration of [missing information]. N-type layer 7;

[0064] The second step involves using wet etching technology to form a platform with a depth of approximately 4µm.

[0065] The third step is to grow a CdTe and ZnS bilayer passivation film 8 on the surface of the mesa using magnetron sputtering technology, with CdTe on the bottom and ZnS on the top, and the thicknesses of CdTe and ZnS are 50nm and 150nm, respectively.

[0066] The fourth step is to remove the double-layer passivation film material at the electrode hole location using hydrochloric acid and dichromic acid solutions.

[0067] The fifth step involves growing the cathode lead 9 and the anode lead 10 using ion beam sputtering to form a Sn / Au double-layer electrode, with Sn on the bottom and Au on top, with a thickness of 20nm / 200nm, forming a good gold-semiconductor contact with mercury cadmium telluride.

[0068] like Figure 4The figure shows the photocurrent versus voltage relationship of the detector without multiplication layer 5 and modulation layer 6 at different incident wavelengths, with other components remaining unchanged. As can be seen from the figure, the photocurrent-voltage curves under illumination conditions of 3 μm, 4 μm, 5 μm, 6 μm, and 7 μm almost overlap, making it impossible to distinguish the responses at different wavelengths. This indicates that without modulation layer 6 to distribute the voltage drop and precisely control the depletion width, the detector cannot selectively gate different absorption depths (corresponding to different wavelengths) by applying an external bias voltage, and therefore lacks electrically programmable wavelength selection functionality.

[0069] like Figure 5 The figure shows the dark current versus voltage relationship of a detector without multiplication layer 5 and control layer 6, where other components remain unchanged. The vertical axis is a logarithmic scale. The figure shows that the dark current of this detector increases exponentially with increasing bias voltage; when the bias voltage reaches approximately -6 volts, the dark current exceeds approximately 10 volts. -3 The voltage exceeds the ampere level, and detector breakdown occurs, preventing the application of higher voltages. This phenomenon indicates that in structures without multiplication layer 5 and modulation layer 6, the high electric field directly affects the absorption region, significantly enhancing high-field leakage mechanisms such as interband tunneling, leading to a rapid increase in dark current. Furthermore, the dark current value in the figure is close to the photocurrent at the corresponding wavelength, indicating that this type of detector has a low signal-to-noise ratio and is unsuitable for reliable avalanche amplification detection at high voltages.

[0070] Figure 6 for Figure 3 (Including detectors with multiplication layer 5 and control layer 6) and Figure 5 The comparison graph (excluding the detector with multiplication layer 5 and control layer 6) shows the dark current levels of the two structures under different bias voltages on the vertical axis, with the vertical axis representing a logarithmic scale. As can be seen from the graph, with the addition of multiplication layer 5 and control layer 6, the high electric field is confined to the multiplication region, and the field enhancement and interband tunneling in the absorption region are significantly suppressed. Therefore, the dark current of the detector is significantly reduced under the same operating bias voltage, enabling the detector to achieve controlled amplification at higher bias voltages without premature breakdown.

[0071] The above results show that the synergistic design of the control layer 6 and the multiplication layer 5 confines the high electric field to a dedicated multiplication region and precisely distributes the voltage drop through the control layer 6, thereby achieving effective decoupling of the absorption-multiplication process: it retains the high sensitivity brought by avalanche multiplication while significantly suppressing the dark current growth and detector breakdown caused by the high field in the absorption region, demonstrating the obvious superiority of this invention in the technical trade-off between bias programmable wavelength selection and low-noise amplification.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. All equivalent changes and modifications made within the scope of the claims of this invention should be considered within the technical scope of this invention.

Claims

1. An electrically programmable mercury cadmium telluride wavelength selective detector based on spatial bandgap gradient, comprising a substrate (1), on which a mesa structure consisting of a P-type layer (2), an absorption layer (3), a buffer layer (4), and an N-type layer (7) are grown sequentially upwards, and a passivation layer (8) is wrapped around the mesa structure, a cathode lead-out terminal (9) is provided in the P-type layer (2), and an anode lead-out terminal (10) is provided in the N-type layer (7). characterized in that The band gap of the absorption layer (3) gradually increases and changes in gradient along the direction from the P-type layer (2) to the buffer layer (4), so that the main absorption positions of different wavelengths of light are distributed at different depths; Between the buffer layer (4) and the N-type layer (7), a multiplication layer (5) and a regulation layer (6) are also grown. The multiplication layer (5) grows on the buffer layer (4), and the regulation layer (6) grows on the multiplication layer (5). The multiplication layer (5) forms a narrow multiplication region inside the detector. The multiplication region is a high electric field region. The multiplication region can trigger controllable impulse ionization within the proposed bias voltage range, thereby limiting the required voltage drop within the multiplication region while maintaining high sensitivity. The control layer (6) forms a specific electric field distribution structure with the multiplication layer (5) and the adjacent absorption layer (3), thereby achieving precise positioning of the depletion boundary and the multiplication region under the applied bias voltage. The applied bias voltage not only changes the field strength and width of the multiplication region, but also makes the spatial distribution of the multiplication region change in a controlled manner within a certain bias voltage range, thereby achieving relative fixation of the position of the multiplication region or controllable adjustment along the depth direction, so that the photogenerated carriers at a specific depth can be collected and multiplied by bias programmable.

2. The probe of claim 1, wherein: The substrate (1) is a zinc cadmium telluride, gallium arsenide, cadmium telluride or silicon substrate.

3. The detector as described in claim 1, characterized in that: The P-type layer (2) is Hg vacancy-doped P-type mercury cadmium telluride, with a thickness in the range 0.3 pm to 1 pm, a Cd content of 0.2 and a doping concentration of .

4. The detector as described in claim 1, characterized in that: The absorption layer (3) is P-type Hg doped with Hg vacancies 1- x Cd x Te alloy, 1.7 µm to 3 µm thick, with a Cd content x varying along the depth with a gradient ranging from 0.20 to 0.35, decreasing with depth, and a doping concentration of .

5. The detector as described in claim 1, characterized in that: The buffer layer (4) is Hg vacancy-doped P-type mercury cadmium telluride, with a thickness ranging from 0.3µm to 0.5µm, a Cd content of 0.40 to 0.43, and a doping concentration of [missing information]. .

6. The detector as claimed in claim 1, characterized in that: The multiplication layer (5) is a P-type mercury cadmium telluride doped with Hg vacancy, with a thickness ranging from 0.3µm to 0.5µm, a Cd content of 0.43 to 0.45%, and a doping concentration of [missing value]. .

7. The detector as claimed in claim 1, characterized in that: The control layer (6) is N-type mercury cadmium telluride, with a thickness ranging from 0.15µm to 0.3µm, a Cd content of 0.43 to 0.45%, and a doping concentration of [missing information]. .

8. The detector according to claim 1, characterized in that: The N-type layer (7) is N-type mercury cadmium telluride, with a thickness ranging from 0.15µm to 0.3µm, a Cd content of 0.43 to 0.45%, and a doping concentration of [missing information]. .

9. The detector according to claim 1, characterized in that: The passivation layer (8) is a CdTe and ZnS double passivation film, with CdTe located in the lower layer and ZnS located in the upper layer, and the thickness ratio of CdTe to ZnS is 1:

3.

10. The detector according to claim 1, characterized in that: The cathode lead-out end (9) and the anode lead-out end (10) are both Cr / Au double-layer electrodes or Sn / Au double-layer electrodes. The ohmic contact layer in contact with the mesa structure is Cr or Sn, and the metal conductive layer is Au. The thickness of Cr or Sn is 0.01μm~0.1μm, and the thickness of Au is 0.1μm~0.6μm. At least two cathode lead-out ends (9) are provided.

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