Modelling of dark currents in LWIR HgCdTe photodiodes

HgCdTe long-wavelength infrared (LWIR) photodiodes have been successfully fabricated using plasma induced junction formation. The performance of the devices were characterised through I-V measurements and analysed by modelling the dark current mechanisms which determine the I-V characteristic. Analytical models were used and a very close fit to the measured data at 80 K was achieved. The model included the effects of diffusion, trap-assisted tunnelling, band-to-band tunnelling, generation-recombination, and surface leakage current. The dark current modelling has identified material defects and non-ideal surface passivation as the factors limiting performance in HgCdTe LWIR photodiodes fabricated using plasma induced junction formation.