Multistep InAs/InAsSb staircase nBn long-wavelength infrared detectors with enhanced charge carrier transport

Gallium-free Type-II superlattices (T2SLs) have emerged as promising candidates for high-performance longwavelength infrared (LWIR) detectors at a high operating temperature. However, InAs/InAsSb barrier detectors suffer from the limited absorption efficiency, resulting in a trade-off between quantum efficiency (QE) and dark current. Here, a nBn LWIR detector based on multistep strain-balanced InAs/InAs0.5Sb0.5 superlattice staircase configuration is proposed. With this configuration, charge carrier transport and collection can be efficiently improved via the multistep staircase valance band, leading to an increased QE from 19.3% to 20.8% at a bias of -0.20 V. As a result, the device with multistep staircase configuration exhibits an improved performance, including a low dark current density of 4.13 x 10-5 A/cm2, high responsivity of 1.23 A/W and peak detectivity reaching 3.10 x 1011 cm & BULL;Hz1/2/W. By optimizing absorbing length of the multistep staircase absorber, the peak QE can be further boosted from 20.8% to 28.4% while maintaining a low dark current level, providing an alternative strategy to improve LWIR T2SL device performance.