Effects of Temperature And

An experimental and theoretical study is reported which successfully achieves agreement between the photoconductive properties exhibited in n-type Hg 0. 6 Cd 0 4 Te and a model based on the theory of minority carrier trapping. Photoconductive properties are described which were measured over a range of temperature and background conditions. The temperature range was from 80 *K to 300 *K; the background ranged from that due to the 300 *K ambient condition to values up to a factor of 102 higher. At the lower temperature and background conditions long average response times and enhanced photoconductive gains depend inversely on the background photon flux. At temperatures above 200 *K the background dependence ceases and the response times approach 10-6 s. At low temperatures asymmetrical rise and decay transient characteristics correspond to neither linear nor quadratic re-combination, while at 300 *K the transients are exponential and indicative of linear recombination. Steady state response measurements reveal a nonlinear relationship between An and the illumination at low temperatures. The small signal responsivity is characterized under varying conditions of temperature and background. These results indicate that minority carrier trapping is the dominant low temperature mechanism. Moreover, it is shown that a single level trap model is inadequate to explain the data. It is shown how the assumption of a uniform continuum of trapping levels achieves better agreement with experiment. The continuum approach is then extended to consider an exponential distribution of trapping states which successfully fits the low frequency res-ponsivity data over the range of temperature and background conditions investigated. Finally, a method for deducing the density of states directly from the data is derived. The results of applying this method show agreement with the exponential density of traps model.