Thermal relaxation of the deposition-induced nonequilibrium state and steady-state defect density in hydrogenated amorphous silicon

초록

We report results on the relaxation of deposition-induced nonequilibrium state and steady-state defect density in undoped hydrogenated amorphous silicon (a-Si:H). The relaxation was studied by monitoring the change of dark conductivity and photoconductivity as a low-substrate-temperature film undergoes thermal annealing. It is found that the time dependence of the relaxation follows a stretched-exponential time law, as observed in the relaxation of the nonequilibrium state induced by various treatments. It is found that the time constant τR and stretched exponent β derived from the relaxation is thermally activated with an activation energy of about 0.94 eV and is given by βT/273 K, respectively. In addition, it is found that the defect density in the steady state is about 2.6×1016 cm-3, and independent of temperature, inconsistent with that expected in the thermal equilibrium theory. © 1994 The American Physical Society.