AC Conductivity of Undoped a-Si:H and µc-Si:H in Connection with Morphology and Optical Degradation

Ac conductivity of a-Si:H and µc-Si:H films is studied experimentally with theoretical consideration. By separating ac conductivity into band, variable range hopping (VRH), band tail multiple hopping and intimate pair hopping conductivities, the effects of the morphology and optical degradation in each type of the conductivities were investigated to elucidate the nature of electronic conduction. Experimental facts on the pair-hopping conductivity seem to be explained in terms of a two-electron correlated barrier hopping (CBH) model between oppositely charged dangling bond pairs located at low-density Si–H alloy regions (voids). Long-range transport (band, multiple hopping, VRH) seems to be related to the percolation through Si clusters and microcrystalline grains, being sensitive to the morphology and Fermi level position.