Effect of dislocations on dark current in LWIR HgCdTe photodiodes

In recent years, Teledyne Imaging Sensors has begun development of Long Wave Infrared (LWIR) HgCdTe Detector Arrays for low background astronomical applications, which have a high percentage of low dark current pixels but a substantial high dark current tail. Characterization of high dark current pixels in these devices has produced I-V curves with unusual behaviors. The typical theories of diffusion current, tunneling current, and even surface current have been unable to accurately model the observed I-V curves. By modeling dislocations in and near the p-n junction as trapping sites and those near the surface as leakage channels, the behavior of these unusual I-V curves is successfully modeled, pointing to the need to reduce the number of these dislocations in order to produce LWIR HgCdTe photodiodes exhibiting very low dark current with sufficient well depth.