1/f noise in ion-implanted and double-layer epitaxial HgCdTe photodiodes

1/f noise in Hg0.7Cd0.3Te photodiodes has been measured as a function of temperature, junction area, diode voltage, and gate bias in order to identify the dominant noise mechanisms. The p-n junctions were formed both by ion implantation and by growth of double-layer epitaxial structures. The LPE base layers were doped with arsenic and the devices were passivated with photochemically deposited SiO2. Two leakage current mechanisms were identified as sources of 1/f noise. Under optimized surface potentials, the 1/f noise was proportional to the depletion-region GR current generated at the surface. This was observed in both double-layer devices in which the leakage current was primarily generated at the depletion-region surface, and in ion-implanted devices in which the leakage current had a bulk depletion-region origin. For nonoptimized gate voltages, where tunneling currents were the dominant leakage mechanism, the noise current was proportional to the tunneling current. Surface, bulk, and photogenerated diffusion currents were not accompanied by significant amounts of 1/f noise. The proportionality factor between the noise current and the depletion-region leakage current for the devices passivated with SiO2 was found to range from one to ten times lower than the values previously reported for ZnS-passivated devices. The results are discussed terms of Handel’s bremsstrahlung model, Kleinpenning’s mobility fluctuation model, and the McWhorter–Anderson–Hoffman surface potential fluctuation model.