Collective phonon interaction and annealing of metastable defects in amorphous semiconductors

Abstract

Abstract In hydrogenated amorphous semiconductors, metastable defects (MSDs) are induced by recombination of non-equilibrium carriers. The isothermal annealing of MSD follows a stretched-exponential time dependence with a dispersion parameter β proportional to the temperature: β=T/T∗. In this study, we observe that the experimental T∗ values are proportional to the lattice optical phonon frequency for a wide collection of hydrogenated amorphous alloys, including undoped a-Ge : H, a-Si : H, a-SiC0.13 : H and a-SiN1.6 : H and n-doped a-Si : H. This result indicates an intrinsic origin for the metastability. We propose a new interpretation of the available data based on a multiphonon-assisted decay of the metastable defects. A large barrier energy E act requires a collective interaction of a large number n=Eact/hωo of localized optical phonons. The number ω(n) of accessible vibrational configurations for a set of n phonons within a finite medium-range interaction volume, is defined as the density of n-phonon...