Tunneling and dark currents in HgCdTe photodiodes

The dc characteristics of front‐illuminated ion‐implanted n⁺ on bulk p‐type Hg_1−xCd_xTe with x≊0.22, operating at 77 K, are modeled with three distinct mechanisms that dominate the dark current: In the zero‐ and low‐bias region, diffusion current is the dominant current down to 60 K. For medium reverse bias, at 77 K, trap‐assisted tunneling produces the dark current and dominates the dark current at zero bias below 50 K. For a high reverse bias, bulk band‐to‐band tunneling dominates. By measuring the temperature dependence of the dc characteristics in the temperature range 65–132 K, the mechanisms are studied and the validity of the modeling is confirmed. The 1/f noise phenomena measured at high reverse bias are correlated with the bulk band‐to‐band tunneling current. The electrical profile of the implanted junction is correlated with the origin of the p‐type conductivity and with the dc characteristics.