Light-enhanced deep deuterium emission and the diffusion mechanism in amorphous silicon

We demonstrate that hydrogen diffusion in hydrogenated amorphous silicon (a-Si:H) is trap controlled and measure a 1.4-eV barrier for deep deuterium emission to a transport level in D-doped a-Si:H. We show that light-enhanced diffusion in a-Si:H is caused by light-enhanced detrapping of H and not by heating of the sample. From our experiments, we obtain estimates of the free-H-diffusion coefficient (3×{}10^-8 cm² s^-1), the mean H displacement between deep trapping events (250 {}), and the other parameters that determine the measured H-diffusion coefficient in a-Si:H.