Evaluation by room-temperature electroreflectance of the 77 K dark-storage time of bulk mercury cadmium telluride measured on metal-insulator semiconductor devices

Abstract

We have studied a set of 14 very carefully characterized samples by spectroscopic ellipsometry, electrolyte electroreflectance (EER), and other measurements, and have measured the 77 K storage time τ of metal-insulator semiconductor (MIS) devices built on these samples. The measured storage times ranged from 6.8 to 130.8 μs. Only the results of the EER measurements showed a correlation with the measured values of τ. We interpret our EER results in terms of a two-phase model consisting of bulk plus very thin, highly defectuous regions, possibly associated with subgrain boundaries. The observed correlation between the values of the incremental linewidth ΔΓ of the thin defectuous regions and the values of the charge-storage lifetimes τ of the MIS devices is excellent and capable of predicting the values of τ. Furthermore, the exact form of the observed correlation is shown to follow immediately from a simple physical model. Correlations between the values of τ and those of other parameters measured by EER were also observed. They suggest a possible simple physical picture for the primary origin of dark current in these devices. This is the first predictive quantitative correlation ever observed between the results of room-temperature optical characterizations of semiconductor materials and the low-temperature electrical performance of devices built on those materials.