Effects of passivation and extraction trap density on the 1/f noise of HgCdTe photoconductive detector

Experimental results are presented for noise voltage and responsivity for a HgCdTe photoconductive detector. Hg_0.8Cd_0.2Te photoconductive detector passivated with Zns/photo-enhanced native oxide shown an improved noise spectral density relative to detector passivated with only ZnS. The low frequency 1/f noise charges have been measured in Hg_0.8Cd_0.2Te photo detector as a function of bias and the effective insulator trap density from the 1/f noise charges was determined at 77 K. It was illustrated that the insulator effective trap densities of stacked passivation and only ZnS passivation are close to 4×10¹⁷ and 9×10¹⁷ cm^-2 eV¹ at 0.4 V bias with 1 msec integration time, respectively. We find that the numerical values of 1/f noise are strongly dependent upon surface passivation properties. From responsivity measurement, it is clear that the sweepout effect is only important at high electrical field. Finally, it is evident that these photo detectors, which passivated with stacked dielectric layers may be useful for focal plane array.