Design of long-wavelength infrared InAs/InAsSb type-II superlattice avalanche photodetector with stepped grading layer

Abstract

Weak response in long-wavelength infrared (LWIR) detection has long been a perennial concern, significantly limiting the reliability of applications. Avalanche photodetectors (APDs) offer excellent responsivity but are plagued by high dark current during the multiplication process. Here, we propose a high-performance type-II superlattices (T2SLs) LWIR APD to address these issues. The low Auger recombination rate of the InAs/InAsSb T2SLs absorption layer is exploited to reduce the dark current initially. AlAsSb with a low k value is employed as the multiplication layer to suppress device noise while maintaining sufficient gain. To facilitate carrier transport, the conduction band discontinuity is optimized by inserting an InAs/AlSb T2SLs stepped grading layer between the absorption and multiplication layers. As a result, the device exhibits excellent photoresponse at 8.4 μm at 100 K and maintains a low dark current density of 5.48 × 10⁻² A/cm². Specifically, it achieves a maximum gain of 366, a responsivity of 650 A/W, and a quantum efficiency of 26.28% under breakdown voltage. This design offers a promising solution for the advancement of LWIR detection.