HOLE DRIFT MOBILITY MEASUREMENTS IN AMORPHOUS SILICON-CARBON ALLOYS

Hole drift mobilities have been measured using photocarrier time-of-fl ight for several hydrogenated amorphous silicon-carbon alloy specimens . We find that, as the band gap increases, the hole drift mobility rem ains essentially constant. The temperature and dispersion properties w ere broadly consistent with hole multiple trapping in the valence band tail. In conjunction with previous drift mobility measurements in hydr ogenated amorphous silicon-carbon alloys and hydrogenated amorphous si licon-germanium alloys, these hole measurements complete a simple patt ern for the effects of band gap modification on drift mobilities: elec tron mobilities decline as the band gap is increased or decreased from 1.75 eV, but hole mobilities are relatively unaffected.