Comparative simulation study of Ga-free and Sb-based mid-infrared photodetectors with barrier engineering

Antimonide (Sb)-based materials are leading the development of low-noise, high-gain avalanche photodiodes for infrared applications. Achieving minimal dark current in a simple p–i–n device structure remains a significant challenge. In this work, we explore the inherent flexibility of the InAs1−xSbx ternary alloy material systems to design the nBn architecture and investigate its performance through barrier engineering. To further explicate the physics of Ga-free detectors, we investigate the transport and dark current performance of nBn designs using three different barriers, including quaternary AlInAsSb, ternary AlAsSb, and binary AlSb material systems while employing InAsSb for the absorber and contact layers. We also calculate several other key transport and optoelectronic parameters, including energy band profiles, carrier density, electric field distribution, electrostatic potential, and absorption coefficient for these designs. Through our comprehensive simulation analysis, we demonstrate that such Ga-free and Sb-based novel device designs effectively minimize the dark current density by confining the electric field inside the barrier, and the current in such detectors is diffusion-limited. We also show that, under specific conditions, the dark current density can be effectively minimized by carefully controlling the thickness of the absorber layer. We not only advance the understanding of the physics behind these materials and devices, but also uncover valuable insights for evaluating and optimizing quaternary, ternary, and binary barrier-based Ga-free nBn structures. This provides a systematic framework to address fundamental challenges and paves the way for future advancements in next-generation mid-wavelength infrared photodetectors.