InAs / GaSb superlattice medium / long wave two-color infrared detector based on nBn structure
By designing an InAs/GaSb superlattice with an nBn structure and optimizing the absorption and barrier layers, the material and fabrication problems of existing mid/long-wavelength dual-color infrared detectors were solved, achieving efficient mid/long-wavelength response and low crosstalk, thus improving the stability and imaging accuracy of the device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-23
- Publication Date
- 2026-03-31
AI Technical Summary
Existing mid/long-wave dual-color infrared detectors face multiple technical barriers in terms of material systems, device architecture, and process control, resulting in high dark current, high crosstalk rate, poor process repeatability, and high cost, making it difficult to achieve high-precision imaging.
An InAs/GaSb superlattice design with an nBn structure is adopted, including a combination of superlattice layers with specific thickness and doping concentration. The absorption layer thickness and barrier layer design are optimized. Mid-/long-wavelength response is achieved by using 14ML InAs/7ML GaSb and 8ML InAs/6ML GaSb superlattices, and epitaxial defects are reduced by using 4ML InAs/7ML GaSb superlattice as a barrier layer.
It achieves high absorption efficiency and low crosstalk in the mid/long wavelength range, reduces dark current, has wide operating temperature range capability, excellent low temperature stability and high-precision imaging performance.
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Figure CN224069047U_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of optoelectronic device technology, specifically relating to a mid / long-wavelength dual-color infrared detector based on an InAs / GaSb superlattice with an nBn structure. Background Technology
[0002] Mid- / long-wave dual-color infrared detectors are core devices in fields such as remote sensing, night vision, and spectral analysis. Their realization mainly relies on HgCdTe alloy materials and InAs / GaSb superlattice systems, but both have significant defects.
[0003] Although HgCdTe alloy materials can achieve dual-color response, the material composition is not uniform and the composition distribution is difficult to control precisely, resulting in high dark current density of the device, low process repeatability, poor low-temperature stability of the device, and easy interface delamination after multiple thermal cycles. The yield has been below 60% for a long time, resulting in high manufacturing costs.
[0004] While the InAs / GaSb superlattice system has advantages such as tunable bandgap and low dark current, traditional device architectures and material designs suffer from the following problems: 1. Short carrier lifetime: Due to material interface defects and Ga-related intrinsic defects, the minority carrier lifetime is generally less than 100 ns, significantly limiting the quantum efficiency of long-wavelength channels; 2. Stress accumulation and lattice mismatch: The thickness of the InAs layer needs to be increased to extend the cutoff wavelength, but the lattice mismatch between InAs and GaSb leads to interface stress accumulation. When the thickness exceeds the critical value (~5 μm), microcracks are easily induced, resulting in an increase in epitaxial defect density; 3. Defects in barrier layer design: Although existing barrier layers (such as AlAsSb / InAsSb composite structures) can suppress crosstalk, the lattice mismatch of heteromaterials exacerbates defect formation, increasing the tunneling current by an order of magnitude under reverse bias.
[0005] The mainstream structure of existing mid / long-wave dual-color infrared detectors is a stacked structure, but its technological development is still limited by multiple bottlenecks in material systems and device architecture.
[0006] Regarding the inherent contradictions in device architecture, there is a contradiction between the thickness of the absorption layer and the wavelength. If the absorption layer is too thin, the light absorption depth in the long-wavelength band will be insufficient, and the responsivity will be too low. If the absorption layer is too thick, stress accumulation will lead to a high lattice mismatch rate. In addition, high-concentration doped contact layers are prone to Fermi level pinning effect, which leads to band bending and a decrease in carrier transport efficiency.
[0007] Regarding the challenges in material growth processes, when using traditional molecular beam epitaxy (MBE) to grow thick superlattices, the interface roughness (RMS) and minority carrier diffusion length deteriorate significantly, which greatly limits the collection efficiency of photogenerated carriers. The lattice mismatch between the single GaSb buffer layer and the long-wavelength absorption layer leads to excessive interface stress at low temperatures, which induces dislocation multiplication and reduces device yield.
[0008] Regarding the challenges of spectral separation and crosstalk suppression, existing technologies rely on external filters or complex readout circuits to achieve dual-color separation, which significantly increases system complexity and cost. Although monolithic integration solutions based on band engineering can simplify the structure, the crosstalk rate of the long-wave and mid-wave channels is still higher than 15%, and the cutoff wavelength adjustment accuracy is low, making it difficult to meet the requirements of high-precision imaging.
[0009] In summary, current mid / long-wave dual-color infrared detectors face multiple technical barriers in terms of material systems, device architecture, and process control, and there is an urgent need for an innovative solution that can synergistically optimize light absorption efficiency, dark current suppression, and process compatibility. Utility Model Content
[0010] To address the technical problems of existing mid / long-wave dual-color infrared detectors, this invention provides a mid / long-wave dual-color infrared detector based on an InAs / GaSb superlattice with an nBn structure. This detector achieves high absorption efficiency and low crosstalk in both mid-wave (3-5μm) and long-wave (8-12μm) dual-band responses, and also features low dark current and wide operating temperature range.
[0011] The technical solution adopted in this utility model is as follows:
[0012] A mid- / long-wave dual-color infrared detector based on an InAs / GaSb superlattice with an nBn structure includes, from bottom to top, a substrate layer, a buffer layer, a bottom contact layer, a long-wave absorption layer, a barrier layer, a mid-wave absorption layer, and a top contact layer.
[0013] The substrate is a GaSb substrate; the buffer layer is an undoped GaSb buffer layer; the bottom contact layer is a 14ML InAs / 7ML GaSb superlattice Si doped layer; the long-wave absorption layer is a 14ML InAs / 7ML GaSb superlattice unintentionally doped (UID) layer; the barrier layer is a 4ML InAs / 7ML GaSb superlattice unintentionally doped layer; the mid-wave absorption layer is an 8ML InAs / 6ML GaSb superlattice unintentionally doped layer; and the top contact layer is an 8ML InAs / 6ML GaSb superlattice Si doped layer.
[0014] Furthermore, the InAs / GaSb superlattice mid / long-wavelength dual-color infrared detector based on the nBn structure also includes two electrodes, located on the upper surfaces of the bottom contact layer and the top contact layer, respectively.
[0015] Furthermore, the thickness of the long-wave absorption layer and the medium-wave absorption layer is 2 μm.
[0016] Furthermore, the Si doping concentration of the bottom contact layer and the top contact layer is 5 × 10⁻⁶. 17 ~1×1018 cm -3 .
[0017] Furthermore, the thickness of the bottom contact layer and the top contact layer is 0.1 μm.
[0018] Furthermore, the thickness of the barrier layer is 0.5 μm.
[0019] Furthermore, the thickness of the buffer layer is 0.3 μm.
[0020] Furthermore, the substrate layer is a Te-doped n-type (001) crystal-oriented GaSb substrate with a doping concentration of 5 × 10⁻⁶. 16 ~2×10 17 cm -3 .
[0021] The beneficial effects of this utility model are as follows:
[0022] 1. This invention proposes a mid- / long-wave dual-color infrared detector based on an InAs / GaSb superlattice with an nBn structure. It utilizes a combination of mid- / long-wave absorption layers of 14ML InAs / 7ML GaSb superlattices and 8ML InAs / 6ML GaSb superlattices to achieve dual-band detection of mid-wave (3-5μm) and long-wave (8-12μm). At the same time, by optimizing the thickness of each layer, the absorption efficiency of the device is improved and crosstalk is effectively suppressed, which is expected to be useful in high-precision imaging applications.
[0023] 2. This invention uses a 4ML InAs / 7ML GaSb superlattice of the same system as a barrier layer, which can effectively avoid the problem of increased epitaxial defect density caused by lattice mismatch with the medium / long wavelength absorption layer, and helps to reduce the dark current of the device.
[0024] 3. The InAs / GaSb superlattice mid / long-wavelength dual-color infrared detector proposed in this invention has a wide temperature range operation capability, maintains a high responsivity at 120K, and has excellent low-temperature stability, which can reduce the dependence on deep cooling equipment. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of the structure of the InAs / GaSb superlattice mid / long-wavelength dual-color infrared detector based on the nBn structure proposed in Embodiment 1 of this utility model;
[0026] Figure 2 The long-wavelength channel light absorption spectrum of the InAs / GaSb superlattice dual-color infrared detector based on the nBn structure proposed in Embodiment 1 of this utility model;
[0027] Figure 3The mid-wavelength channel light absorption spectrum of the InAs / GaSb superlattice mid / long-wavelength dual-color infrared detector based on the nBn structure proposed in Embodiment 1 of this utility model;
[0028] Figure 4 The long-wavelength channel response curve of the InAs / GaSb superlattice dual-color infrared detector based on the nBn structure proposed in Embodiment 1 of this utility model;
[0029] Figure 5 The mid-wave channel response curve of the InAs / GaSb superlattice mid / long-wave dual-color infrared detector based on the nBn structure proposed in Embodiment 1 of this utility model;
[0030] Figure 6 This is a superimposed diagram of the dual-channel response of the InAs / GaSb superlattice mid / long-wavelength dual-color infrared detector based on the nBn structure proposed in Embodiment 1 of this utility model. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and represented herein can typically be arranged and designed in various different configurations.
[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0033] Example 1
[0034] This embodiment provides a mid- / long-wavelength dual-color infrared detector based on an InAs / GaSb superlattice with an nBn structure, as shown in the following structure. Figure 1 As shown, it includes, from bottom to top, a substrate layer, a buffer layer, a bottom contact layer, a long-wave absorption (long-wave channel) layer, a barrier layer, a mid-wave absorption (mid-wave channel) layer, and a top contact layer, as well as two electrodes located on the upper surfaces of the bottom contact layer and the top contact layer, respectively.
[0035] The substrate is a Te-doped n-type (001) oriented GaSb substrate with a thickness of 500 μm and a doping concentration of 1 × 10⁻⁶. 17 cm -3 Surface roughness RMS≤0.2nm.
[0036] The buffer layer is an undoped GaSb buffer layer with a thickness of 0.3 μm, obtained by epitaxial growth on the surface of the substrate, and has a lattice mismatch rate Δa / a < 0.01%.
[0037] The bottom contact layer is a 14ML InAs / 7ML GaSb superlattice Si-doped layer, with a period repeat of 50 times, a thickness of 0.1μm, and a Si doping concentration of 1×10⁻⁶. 18 cm -3 .
[0038] The long-wavelength absorption layer is a 14ML InAs / 7ML GaSb superlattice unintentionally doped layer with a period repeat of 285 times and a thickness of 2μm.
[0039] The barrier layer is a 4ML InAs / 7ML GaSb superlattice unintentionally doped layer with a period repeat of 65 times and a thickness of 0.5μm.
[0040] The mid-wave absorption layer is an 8ML InAs / 6ML GaSb superlattice unintentionally doped layer with a period repeat of 320 times and a thickness of 2μm.
[0041] The top contact layer is an 8ML InAs / 6ML GaSb superlattice Si-doped layer, with a period repeat of 20 times, a thickness of 0.1 μm, and a Si doping concentration of 1 × 10⁻⁶. 18 cm -3 .
[0042] The electrode is made of Au.
[0043] Based on Silvaco TCAD (a semiconductor process and device simulation tool), the band structure of the InAs / GaSb superlattice mid / long-wavelength dual-color infrared detector based on the nBn structure proposed in this embodiment was simulated. The conduction band shift ΔE of the barrier layer was determined. C =0.38eV, valence band aligned ΔE V ≈0eV indicates that the barrier layer forms an electron monopole block between the long-wavelength absorption layer and the mid-wavelength absorption layer; the conduction band bottom E of the long-wavelength absorption layer C = -0.12 eV (relative to the valence band top of GaSb), the conduction band bottom of the mid-wave absorption layer E C =0.16eV, which ensures the directional transport of photogenerated carriers.
[0044] Under simulated conditions of a blackbody radiation source of 500K and a wavelength range of 2–12 μm, the absorption spectrum of the long-wavelength absorption layer (long-wavelength channel) in this embodiment was obtained, as follows: Figure 2As shown, the absorption peak intensity at 10.7 μm is 4626 (au), and the absorption coefficient α = 2.8 × 10⁻⁶. 4 The lower limit of the 50% absorption cutoff wavelength is 6.9 μm, and the upper limit is 10.5 μm.
[0045] Under simulated conditions of a blackbody radiation source of 800K and a wavelength range of 2–12 μm, the absorption spectrum of the mid-wave absorption layer (mid-wave channel) in this embodiment was obtained, as follows: Figure 3 As shown, the absorption peak intensity at 4.4 μm is 4615 (au), and the absorption coefficient α = 3.1 × 10⁻⁶. 4 The lower limit of the 50% absorption cutoff wavelength is 3.1 μm and the upper limit is 7.8 μm.
[0046] Under operating conditions of 120K temperature and -0.2V bias, the response curve of the long-wavelength absorption layer (long-wavelength channel) in this embodiment was obtained, as shown below. Figure 4 As shown, the responsivity at the peak response of 10.7 μm is 1.21 A / W, and the lower limit of the 50% response cutoff wavelength is 6.9 μm, while the upper limit is 10.5 μm.
[0047] Under operating conditions of 120K temperature and 0.1V bias, the response curve of the mid-wave absorption layer (mid-wave channel) in this embodiment was obtained, as shown below. Figure 5 As shown, the responsivity at the peak response of 4.4 μm is 1.29 A / W, and the lower limit of the 50% response cutoff wavelength is 3.1 μm, while the upper limit is 7.8 μm.
[0048] based on Figure 4 and Figure 5 The superposition of these signals yields the dual-channel response superposition diagram of the InAs / GaSb superlattice mid / long-wavelength dual-color infrared detector based on the nBn structure proposed in this embodiment, as shown below. Figure 6 As shown, the visible mid-wave absorption layer (mid-wave channel) Figure 6 The effective wavelength range (denoted as MIR) is 3.1–7.8 μm, and the long-wave absorption layer (long-wave channel) is also included. Figure 6 The effective wavelength range of the medium-wave (LIR) detector is 6.9–10.5 μm, and the overlapping wavelength range is 6.9–7.8 μm. The integral responsivity of the long-wave signal in the medium-wave band accounts for 12.1%, while that of the medium-wave signal in the long-wave band accounts for 9.8%. Therefore, the calculated overall crosstalk rate is only 12.1%, indicating that the InAs / GaSb superlattice medium / long-wave dual-color infrared detector based on the nBn structure proposed in this embodiment has excellent crosstalk suppression effect.
[0049] Example 2
[0050] This embodiment provides a mid- / long-wavelength dual-color infrared detector based on an InAs / GaSb superlattice with an nBn structure. The only difference between this embodiment and Embodiment 1 is that the Si doping concentration of the bottom and top contact layers is adjusted to 5 × 10⁻⁶. 17 cm -3 Other structures and materials remain unchanged.
[0051] The above embodiments are only for illustrating the principles and advantages of this utility model, and are not intended to limit this utility model. They are only for helping to understand the principles of this utility model. The protection scope of this utility model is not limited to the above configurations and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the disclosed technology without departing from the essence of this utility model, but they are still within the protection scope of this utility model.
Claims
1. An InAs / GaSb superlattice mid / long-wave dual-color infrared detector based on an nBn structure, characterized in that, The substrate layer, the buffer layer, the bottom contact layer, the long-wave absorbing layer, the barrier layer, the medium-wave absorbing layer and the top contact layer are sequentially arranged from bottom to top. The substrate layer is a GaSb substrate; the buffer layer is a non-doped GaSb buffer layer; the bottom contact layer is a 14ML InAs / 7ML GaSb superlattice Si doped layer; the long-wave absorbing layer is a 14ML InAs / 7ML GaSb superlattice non-intentionally doped layer; the barrier layer is a 4ML InAs / 7ML GaSb superlattice non-intentionally doped layer; the medium-wave absorbing layer is an 8ML InAs / 6ML GaSb superlattice non-intentionally doped layer; and the top contact layer is an 8ML InAs / 6ML GaSb superlattice Si doped layer.
2. The nBn structure based InAs / GaSb mid / long wave dual-color infrared detector according to claim 1, wherein, The nBn structure-based InAs / GaSb superlattice middle / long-wave dual-color infrared detector further comprises two electrodes respectively located on the upper surfaces of the bottom contact layer and the top contact layer.
3. The nBn-based InAs / GaSb superlattice mid / long-wave dual-color infrared detector according to claim 1, characterized in that, The thicknesses of the long-wave absorbing layer and the medium-wave absorbing layer are 2 μm.
4. The nBn-based InAs / GaSb superlattice mid / long wave dual-color infrared detector according to claim 1, wherein, The thicknesses of the bottom contact layer and the top contact layer are 0.1 μm.
5. The nBn structure based InAs / GaSb mid / long wave dual-color infrared detector according to claim 1, wherein, The thickness of the barrier layer is 0.5 μm.
6. The nBn structure based InAs / GaSb mid / long wave dual-color infrared detector according to claim 1, wherein, The thickness of the buffer layer is 0.3 μm.