THEORY OF DISPERSIVE RELAXATION IN AMORPHOUS-SEMICONDUCTORS

A theoretical derivation is given to the empirical formula delta-n(t) = delta-n(0)K(nu-c(t))-1 + alpha exp [-(t/tau-eff)alpha] for dispersive relaxation of photoconductivity and photoluminescence in amorphous semiconductors of which the power law t-1 + alpha also forms a limiting case. Limits of validity of the formula have been brought out and higher order correction terms have been obtained. At higher excitations or longer times saturation effect becomes important and a quasi-equilibrium between free and trapped charges can be assumed. This gives t-1/1 - alpha decay for the later part of the transient.