Annealing of metastable defects in hydrogenated amorphous silicon

Abstract

The annealing process of light-induced metastable dangling-bond states in hydrogenated amorphous silicon is studied using the analysis presented in the preceding paper for electron-spin-resonance transients. The annealing kinetics are monomolecular, with a thermally activated decay rate R=${\nu }_0$exp(-$E_a$/${\mathrm{kT}}_A$). The decay curves of the metastable defects in pure, UHV-deposited a-Si:H and in a-Si:N,H a-Si:C,H and a-Si:O,H with impurity contents between 1 and 20 at.?are analyzed in terms of a well-defined prefactor, ${\nu }_0$, and a broad distribution of thermal activation energies, N($E_a$). Both ${\nu }_0$ and N($E_a$), depend in a characteristic way on the density and the chemical nature of the impurities present in a sample. Moreover, a strong correlation between ${\nu }_0$ and N($E_a$) similar to the Meyer-Neldel rule for the conductivity in a-Si:H is observed. Implications of the experimental results for the intrinsic or extrinsic nature of the metastable defects and possible annealing mechanisms are discussed.