Analysis of transient photoconductivity in CdSe:Cu:Cl thin films

A number of interesting transient phenomena, occurring in CdSe: Cu: Cl thin films, exhibiting superlinear photoconductivity, are described: the typical S-shaped current rise, the exponential decay, the inversely proportional dependence of rise time on illumination level, the illumination independent decay time, the influence of bias illumination and pulse frequency on the current rise and decay curves, and the possibility to influence the rise and decay time through the application of a potential to a field-plate. A simple, analytical model for these transients, based on the crude two-level model for superlinear photoconductors, is developed. The model explains the observed behaviour qualitatively and, to a certain degree, even quantitatively. Using this model, the value of the electron capture cross section of the sensitizing centres is estimated from the experimental results. The resulting value of 1.9 x 10(-19) cm2 falls in the range of the values reported elsewhere