Spatially resolved space-charge density in the hydrogenated amorphous silicon Schottky barrier from surface photovoltage measurements

A procedure is developed to derive the differential capacitance of the hydrogenated amorphous silicon (a-Si:H) Schottky barrier from surface photovoltage measurements. An algorithm for deducing the spatial variation of the space-charge density, and of the band-gap density of states, from the frequency-dependent capacitance spectrum, is proposed and implemented for undoped a-Si:H. The space-charge density and the density of states near the Fermi level are found to span three orders of magnitude, falling below 1015 cm−3 and 1016 cm−3 eV−1, respectively, into the bulk of the Pt/a-Si:H Schottky barrier.