Dark currents in HgCdTe photodiodes passivated with ZnS/Cds

Experimental and theoretical results are presented for current-voltage and dynamic resistance-voltage characteristics of Hg1-xCdxTe ion-implanted p-n junction photodiodes with x approximate to 0.22 passivated with ZnS/CdS lay ers. By measuring the temperature dependence of the de characteristics in t he temperature range 25-140 KI the dark current mechanisms are studied and the validity of the modeling is confirmed. It was found that the dark curre nts can be represented with three current components over a broad range of voltage and temperature. At high temperature (>90 K) and in low reverse bia s region, the diffusion current dominates. On the other hand, at medium tem perature (40-80 K) and medium reverse bias (<-0.15 V), trap-assisted tunnel ing plays an important role. At low temperature (<40 K) and in the medium r everse bias region (<-0.15 V), band-to-band tunneling is the by leakage cur rent source. However, when the temperature is further lowered to 25 K and t he applied reverse bias is very small (-0.15 to 0 V), the band-to-hand tunn eling current will be ruled out and the trap-assisted tunneling mechanism d ominates again. (C) 1999 The Electrochemical Society. S0013-4651(98)06-100- 7. All rights reserved.