Transient decay from the steady state in the photoconductivity of amorphous semiconductors

We introduce a modification to the theory developed by G. J. Adriaenssens, S. D. Baranovskii, W. Fuhs, J. Jansen, and ij. Oktu [Phys. Rev. B 51, 9661 (1995)] for the initial decay of the photoconductivity in amorphous semiconductors. With the same physical model and application of the concepts of multiple trapping we derive a theory based upon an emission-rate analysis for the decaying free electron density. We obtain an easy-to-use analytical expression for exponential band tails that links the decay characteristics to the band-tail parameter. A comparison with results from full numerical solutions confirms the validity of our analytical approach and the improvement with respect to the results by Adriaenssens et al. We also present solutions, supported by numerical modeling, that relate the power-law exponents for the generation rate dependence of the steady-state photoconductivity with that of the response time for the decay. [S0163-1829(98)06847-7].