Design and simulation of mid-wavelength InAs/GaSb type-II superlattice avalanche photodiodes

InAs/GaSb type-II superlattice (T2SL) avalanche photodiodes (APDs) are particularly well-suited for low-light detection and quantum communication due to their enhanced sensitivity. However, their performance is significantly impacted by dark current and breakdown voltage characteristics. Here, we explore the performance of T2SL APDs by analysing the relationship between the structural parameters of the absorption, charge, and multiplication layers, utilizing Silvaco software and the equivalent materials method. To enhance the device's performance, we integrated a high-doping AlAsSb charge layer into the separate absorption and multiplication (SAM) structure, constructing a SACM (separate absorption, charge, and multiplication) architecture. Simulation results show that the optimized SAM APD achieves a penetration voltage of 24.7 V and a breakdown voltage of 36.5 V. Notably, the insertion of the charge layer effectively reduced the device's dark current from 10^-7 to 10^-9 A. At an operating temperature of 300 K, the SACM APD demonstrates a gain of 73.4 with a reverse bias voltage of 35 V, surpassing the performance of the SAM structure. These findings provide critical insights for the design of high-performance mid-wave infrared detectors, highlighting the potential of T2SL-APDs in achieving high gain and low dark current.