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.