Hole drift mobility measurements in amorphous silicon-carbon alloys

Hole drift mobilities have been measured using photocarrier time-of-flight for several hydrogenated amorphous silicon-carbon alloy specimens. We find that, as the band gap increases, the hole drift mobility remains essentially constant. The temperature and dispersion properties were broadly consistent with hole multiple trapping in the valence bandtail. In conjunction with previous drift mobility measurements in hydrogenated amorphous silicon-carbon alloys and hydrogenated amorphous silicon-germanium alloys, these hole measurements complete a simple pattern for the effects of band gap modification on drift mobilities: electron mobilities decline as the band gap is increased or decreased from 1.75 eV, but hole mobilities are relatively unaffected.