Simulation of dark current characteristics of type-II InAs/GaSb superlattice mid-wavelength infrared p–i–n photodetector

Abstract For photosensitive devices such as infrared (IR) photodetectors, dark current is an important mechanism limiting the performance because it causes a decrease in the signal-to-noise ratio and the responsivity. The main objective of this work is to understand and analyze the InAs/GaSb type-II superlattice (SL) IR photodiode using a device simulator especially focusing on the dark current characteristics. Physical parameters such as the effective density of states and the effective masses are extracted from the k · p band calculation, and included into a two-dimensional device simulator based on the drift-diffusion model. Simulation results demonstrate that the leakage current of the IR photodiode depends on the SL thickness ratio even with the same cut-off wavelength. In the low reverse bias conditions, the “InAs-rich” SL detectors exhibit smaller dark current than the “GaSb-rich” ones, which originates from the difference in the intrinsic carrier density. On the other hand, under the higher voltage and the higher doping level, the larger effective mass of “GaSb-rich” SL can suppress the dark current caused by the tunneling-related leakage mechanisms.