Measurement of carrier lifetime in materials exhibiting anomalous dispersion

Abstract

Electronic transport in disordered semiconductors frequently has an anomalous degree of dispersion, arising from the fact that charge carriers interact with localised states having a broad spread of release time constants. The time-of-flight technique, which is the most common vehicle for studying the phenomenon, is also used to determine carrier lifetimes prior to recombination. However, there has been no detailed study of the effects which anomalous dispersion phenomenon may have in respect to such lifetime measurements. In this paper, the initial results of such an examination, conducted using Monte Carlo numerical simulation procedures, are presented. It is demonstrated that, if performed without considerable care, lifetime measurements are capable of yielding extremely misleading results. Further, the precautions are outlined which are required if meaningful data are to be obtained.