Determination of the Density of States in a-SiC:H from Transient Photoconductivity

Abstract

AbstractIn order to fill the gap of little knowledge about their details, the density of states distributions (DOS) in the upper half of the band gap were determined for a series of wellcharacterised amorphous hydrogenated silicon carbide samples with Tauc gaps between 1.78 and 1.94 eV. A DOS spectroscopic technique, based on the Fourier transform of time-sampled transient photocurrents, allowed the DOS determination on an absolute scale for a wide energy range. The DOS increases in the band tail region with carbon content. It exhibits a minimum at about 0.5 eV which is followed by a defect structure at deeper energies, the density of which also increases with C-content. We find a decreasing time-dependent drift mobility for larger C-content consistent with the lower transit time-determined drift mobility in time-of-flight.