Modeling and simulation of long-wave infrared InAs/GaSb strained layer superlattice photodiodes with different passivants

Current–voltage characteristics of long-wave infrared (LWIR) InAs/GaSb strained layer superlattice photodiodes (cut-off wavelength ∼10 μm), passivated with different surface passivants, have been modeled and simulated using ATLAS software from SILVACO. The simulated results are fitted to previous experimental results obtained on unpassivated devices and those passivated by silicon-dioxide (SiO2), silicon nitride (SixNy) and zinc sulfide (ZnS). Surface parameters in terms of surface recombination velocity, shunt resistance and interface trap density are extracted for different passivants. The performance of silicon-dioxide passivated diode is solely dominated by a shunt leakage path with a shunt resistance value of 0.56 Ω-cm2. Extracted electron and hole surface recombination velocities have values of 105 cm/s and 107 cm/s for unpassivated, 103 cm/s and 105 cm/s for SixNy passivated and 102 cm/s and 103 cm/s for ZnS passivated devices. Interface trap density follows a similar trend with values of 1015 cm−2, 8.5 × 1014 cm−2 and 1010 cm−2 for unpassivated, SixNy passivated and ZnS passivated devices respectively. The suitability and limitations of the simulation tool are discussed.