Study on planar junction infrared detectors based on InAs/GaSb type-II superlattices

Abstract

InAs/GaSb type-II superlattice infrared detectors, with their advantages of tunable bandgap and high material uniformity, have become a preferred material for mid-infrared imaging detectors. Conventional superlattice infrared photodetectors predominantly employ mesa architectures. In contrast, planar junction configurations offer higher fill factors at reduced pixel dimensions while mitigating etch-induced leakage currents, rendering them promising alternatives. Nevertheless, research on such structures remains scarce in the literature. This study presents Si-implanted planar junction photodetectors based on InAs/GaSb type-II superlattices, achieved through optimised device design, fabrication, and systematic characterisation. X-ray diffraction (XRD) measurements indicate that the overall crystalline quality of the material remains intact mainly following post-implantation annealing, and spectral measurements verify the mid-wavelength infrared (MWIR, 3–5 μm) photoresponse. Performance tests further showed that the dark current of the device is related to the area of the implantation window, which decreases as the implantation window area increases. Subsequently, the LBIC laser-induced detection system was used to characterise the optical response distribution of the InAs/GaSb superlattice planar junction device at 77 K and to fit the signal decay curve outside the junction region. The findings indicate that the photosensitive region expanded by 5.4 ± 0.16 μm after implantation, demonstrating the presence of lateral carrier diffusion in the superlattice material. The results of this study show the feasibility of the planar junction design of the mid-infrared focal plane array.