Determination of the gap-state distribution of hydrogenated amorphous silicon alloys from sub-band-gap absorption measurements

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Abstract
The sub-band-gap absorption of undoped hydrogenated amorphous silicon alloys has been measured to obtain the distribution of gap states. Since the absorption is governed by the convolution of the initial and final densities of states for the optical transitions, it was found that small structures in the gap-state distribution cannot be discerned from these measurements. A good fit to the experimental data can be obtained both with and without a peak in the gap-state distribution. This explains the discrepancies in the literature regarding the location of the dangling-bond peak in undoped samples as obtained from sub-band-gap absorption measurements.