Stepped absorber engineering in nBp InAs/GaSb type-II superlattice MWIR detector

We conducted a study to optimize the performance of a mid-wave infrared detector featuring a stepped absorption layer within an nBp type-II superlattice (T2SL) structure. Through numerical simulations, we investigated the effect of the number of absorption regions and the conduction band offset (ΔE_c) on the device's electrical performance, including the dark current density and quantum efficiency (QE) of nBp mid-wave infrared (MWIR) detectors. Based on semiconductor physics, including the energy band structure, we analyzed and explained the underlying mechanisms of these effects. Ultimately, we summarized a method to enhance QE. This mid-wave infrared detector employs three stepped absorption structures designed to effectively reduce J_dark and improve the optical response. The simulation results show that for our optimized InAs/GaSb stepped absorption layer mid-wave infrared detector, under the conditions of 150 K and -0.2 V bias voltage (V_bi), J_dark can reach 5.19 × 10^-3 A/cm², representing a reduction in J_dark by approximately 1.3 times. Additionally, at 150 K and V_bi = -0.2 V, when the wavelength is 4 μm, the QE is 54%, which is an increase of about 13% compared to the QE of the uniform absorption region structure (U).