Time photocurrent response and the density of localised states in disordered semiconductors

The Time Photocurrent Response (TPR) of a disordered semiconductor to a step-like super-gap excitation is examined by numerical simulation under the assumption of one carrier (electron) multiple-trapping and transport, using exponential and featured model density of localised states g(E). A 'plateau' feature in the TPR, followed by a rapid increase and a subsequent turn over to a steady state level, is observed. This is correlated to the Gaussian 'bump' feature of g(E) by studying the relative change with time of the net trapping and recombination rates. The simulation results are validated for a typical photosensitive disordered semiconductor, the a-SiH.