Published online by Cambridge University Press: 25 February 2011
The thickness dependence of the sub-gap optical absorption in plasma-deposited hydrogenated amorphous silicon is carefully studied by photo-thermal deflection spectroscopy. The deep-level defect concentration decays from the top surface into the bulk where it approaches the thermal equilibrium defect density. This defect profile is interpreted in terms of the annealing, during growth, of growth-induced surface defects. It is also shown that the defect profile is compatible with the known growth-temperature dependence of the average defect density in amorphous silicon.