We have studied the dependence of the photoconductivity σp on photocarrier generation rate G in intrinsic a-Si:H at 300K between G=1012cm-3s-1 and 1028cm-3s-1. Below a certain value Go, we find σo=AGγ with γ=0.9±0.05 and the values of A vary considerably with defect concentration Nd which signifies monomolecular recombination through defects. Above Go the recombination is bimolecular, γ=0.5±0.02 and A=(6±3) ×10-15Ω-1cm 1/2 s 1/2 is independent of Nd. The transition value Go is about 3×1020cm-3s-1 for high quality annealed a-Si:H and increases with Nd. A simulation of σp(G) assuming conduction in and recombination from extended states fits our experiments within a capture coefficient Ct=(6±2)×10-9cm3s-1 of carriers to their opposite tail states. Our Ct is close to the value (5±2)×10-9cm3s-1 obtained from optical measurements but higher than (0.5±0.1)×10-9cm3s-1 determined from photoelectric studies. Below T=150K our model calculations overestimate σp because the tunneling transitions, becoming important for recombination and conduction, are neglected.
|Number of pages||6|
|Journal||Materials Research Society Symposium - Proceedings|
|Publication status||Published - 1996|
|Event||1996 Materials Research Society Spring Meeting - San Francisco, United States|
Duration: 8 Apr 1996 → 12 Apr 1996