Mid-wave infrared (MWIR) detectors based on InAs/GaSb type-II superlattices (T2SLs) are increasingly used in defense, environmental monitoring, astronomy, and other fields due to their high sensitivity and tunable bandgap. A key advantage of T2SL detectors is their tunable bandgap, which can be adjusted by controlling the thickness of the superlattice layers rather than altering the material composition. Unlike traditional HgCdTe detectors, where bandgap tuning depends on changes in chemical composition that can lead to lattice mismatch and reduced material quality, T2SLs maintain structural stability and high crystal quality while enabling flexible wavelength detection. However, T2SL detectors face significant challenges, particularly in the areas of high dark current, short carrier lifetimes, and high interface state density. These factors contribute to noise and reduce the overall signal-to-noise ratio, limiting the detectivity and sensitivity of the devices. Dark current, which arises from unwanted carrier recombination and tunneling, is a major issue that degrades the performance of MWIR detectors by increasing noise and reducing detection accuracy, especially at low signal levels. In addition, fast carrier recombination and short lifetimes limit the effectiveness of these detectors as they reduce the time available for collecting photo-generated carriers, leading to lower responsivity and quantum efficiency. To address these issues, we investigate the introduction of electron and hole barrier layers into InAs/GaSb T2SL infrared detectors to suppress dark current and enhance overall device performance. Electron and hole barriers are designed to block majority carriers, reducing recombination and tunneling currents that contribute to high dark current while allowing minority carriers to move freely for signal detection. By optimizing the thickness and doping concentration of these barrier layers, it is possible to significantly reduce dark current without compromising other critical performance parameters, such as responsivity and specific detectivity.

To analyze the influence of electron and hole barrier layers, SILVACO’s ATLAS software is used for simulating the InAs/GaSb T2SL infrared detectors. The nBn and pBp structures are designed with electron-blocking and hole-blocking layers, respectively. Simulations are conducted to investigate the influence of different barrier layer thicknesses (50, 100, 150, 200 nm) and doping concentrations (1×10¹⁵, 4×10¹⁵, 7×10¹⁵, 1×10¹⁶ cm^-3) on device performance. The simulation accounts for the primary dark current mechanisms, including diffusion, generation-recombination (G-R), and tunneling currents. The focus is on understanding how these factors influence dark current density, peak responsivity, and specific detectivity at different bias voltages and temperatures.

The results show that as the barrier thickness and doping concentration increase, dark current density decreases. The optimal values for both nBn and pBp devices are achieved with a barrier thickness of 0.1 μm and a doping concentration of 1×10¹⁵ cm^-3. Under stable bias at -0.5 V and at liquid nitrogen temperature (77 K), the dark current density of the nBn device is 3.53×10^-7 A/cm², with a peak responsivity of 1.62 A/W at a wavelength of 3.5 μm, a cutoff wavelength of 4.9 μm (50%), and a peak efficiency of 62.09% at 2.5 μm, which results in a specific detectivity of 3.41×10¹² cm·Hz^1/2·W^-1. For the pBp device, the dark current density is 4.51×10^-7 A/cm², with a peak responsivity of 1.68 A/W at 3.8 μm, a cutoff wavelength of 5.3 μm (50%), a peak efficiency of 63.77% at 2.1 μm, and a specific detectivity of 3.12×10¹² cm·Hz^1/2·W^-1(Table 2).

The introduction of electron and hole barrier layers in InAs/GaSb T2SL infrared detectors significantly improves device performance by reducing dark current and enhancing responsivity. The effects of different barrier layer thicknesses and doping concentrations on dark current are investigated. It is found that increasing the barrier layer thickness reduces trap-assisted tunneling current, thus lowering the dark current. An increase in the barrier layer doping concentration narrows the depletion region in the absorption layer and influences its band structure. An increase in the absorption layer thickness significantly affects the device’s photoresponsivity. The performance of the two detectors is comparable. The nBn detector, due to its higher barrier layer, further reduces tunneling probability, resulting in slightly lower dark current density and higher specific detectivity. On the other hand, the pBp detector, having electrons as minority carriers, benefits from a longer diffusion length, which facilitates the collection of photogenerated carriers and provides higher carrier mobility, exhibiting superior performance in terms of photoresponsivity and quantum efficiency. Both nBn and pBp-type infrared detectors achieve detection by blocking majority carriers while allowing photogenerated carriers to pass through.