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.