TRAPPING AND RECOMBINATION IN AMORPHOUS HYDROGENATED SILICON STUDIED BY DUAL-BEAM-MODULATED PHOTOCONDUCTIVITY

The frequency-dependent spectrum of dual-beam-modulated photoconductivity reveals that various processes contribute to steady-state photoconductivity in undoped a-Si: H. These are (1) electron thermal emission from doubly-occupied dangling bonds, (2) electron thermal emission from localized states of the conduction-band tail, and (3) quenching of photoconductivity which proceeds by reducing the density of electrons trapped on dangling bonds. These results are obtained on the basis of a model which in particular allows the coefficient γ characterizing the generation rate dependence of photoconductivity (σp) to be related to the coefficients γi(i = 1-3) characterizing processes 1-3: γ =α1 γ1+ α2 γ2 – α3 γ3, where αi is a dimensionless parameter describing the relative contribution of process i. The temperature and the photogeneration rate dependences of these processes studied in the annealed and in the light-soaked states are used to identify the nature of the quenching process. © 1990 Taylor & Francis Ltd.