Study of Trapping and Recombination in a-Si:H by Means of Infrared Enhancement Spectra of Photoconductivity

IR re-excitation of non-equilibrium carriers in undoped a-Si:H has been used to probe the profile of the distribution of deep traps. In a dual-beam experiment, after turning off a pump light, the trapped carriers are re-excited by an IR probe light which causes the photoconductivity(PC) to pass through a maximum, σmax, before settling down towards its steady state value, σs. σmax depends on the time interval td between turning off the pump light and turning on the probe light in a manner Δσ=σmax−σs∞td−α(T) Based on the multiple trapping (MT) model, the distribution of deep traps has been deduced from the temperature dependences of α(T).