STRETCHED-EXPONENTIAL RELAXATION MODELED WITHOUT INVOKING STATISTICALDISTRIBUTIONS

Relaxation phenomena in disordered systems are often described by stre tched exponentials; such behavior has traditionally been explained by invoking statistical distributions. In hydrogenated amorphous silicon, the relaxation has been associated with dispersive diffusion of hydro gen, related to a distribution of energies for trap states and barrier heights. Here we show that invoking such energy distributions is unne cessary; a treatment of hydrogen motion which includes retrapping lead s to a functional form of the decay curve which closely resembles a st retched exponential, and provides an excellent fit to experimental dat a. The implications of the new microscopic model are discussed.