Comparative study on dark current mechanisms of n-on-p and p-on-n long-wavelength HgCdTe infrared detectors

Abstract

The dark current density versus voltage (J-V) curves of long-wavelength mercury cadmium telluride (HgCdTe, MCT) infrared detectors with planar n-on-p and p-on-n structures are measured and compared in this study. The dark currents are decomposed into diffusion, generation–recombination (GR), trap-assisted tunneling (TAT), band-to-band tunneling (BBT) and shunt current for the two types of devices. It was found that the dark current is dominated by diffusion current at -0.05 V in the temperature range of 55–130 K for both of the two devices. Due to the longer minority carrier lifetime, the diffusion current of p-on-n device is suppressed and the total dark current is around one order of magnitude lower than that of n-on-p device at small reverse bias voltage. The tunneling current becomes the main ingredient of dark current at -0.3 V when the operating temperature is lower than 65 K. Because of the higher trap density in the depletion region, the TAT current is more obvious for n-on-p device. The larger donor and acceptor concentrations lead to a larger BBT current of p-on-n device.