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

Experimental results are presented for the noise voltage and responsivity for a HgCdTe photoconductive detector. Hg_0.8Cd _0.2Te photoconductive detectors passivated with ZnS/photo-enhanced native oxide show an improved noise spectral density relative those passivated with ZnS only. The low frequency 1/f noise charges have been measured in the photodetectors as a function of bias and the effective insulator trap density from the 1/f noise charges is determined at 77 K. It is illustrated that the insulator effective trap densities of stacked passivation and ZnS-only passivation are close to 4×10¹⁷ and 9×10¹⁷ cm^-2 eV ¹ 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 measurements, it is clear that the sweepout effect is only important at high electrical field. Finally it is evident that photodetectors passivated with stacked dielectric layers, may be useful for focal plane array applications