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Comparison of experiment and theory of the photoconductivity of a-Si:H up to a generation rate of 10{sup 28}cm{sup -3}s{sup -1}

Book ·
OSTI ID:527714
;  [1]; ;  [2]
  1. Univ. of Chicago, IL (United States). James Franck Inst.
  2. FORTH, Crete (Greece). Inst. of Electronic Structure and Laser
The authors have studied the dependence of the photoconductivity {sigma}{sub p} on photocarrier generation rate G in intrinsic a-Si:H at 300K between G = 10{sup 12}cm{sup {minus}3}s{sup {minus}1} and 10{sup 28}cm{sup {minus}3}s{sup {minus}1}. Below a certain value G{sub o}, they find {sigma}{sub o} = AG{gamma} with {gamma} = 0.9{+-}0.05 and the values of A vary considerably with defect concentration N{sub d} which signifies monomolecular recombination through defects. Above G{sub o} the recombination is bimolecular, {gamma} = 0.5{+-}0.02 and A = (6{+-}3) {times} 10{sup {minus}15}{Omega}{sup {minus}1}cm{sup 1/2}s{sup 1/2} is independent of N{sub d}. The transition value G{sub o} is about 3 {times} 10{sup 20}cm{sup {minus}3}s{sup {minus}1} for high quality annealed a-Si:H and increases with N{sub d}. A simulation of {sigma}{sub p}(G) assuming conduction in and recombination from extended states fits the experiments within a capture coefficient C{sub t} = (6{+-}2) {times} 10{sup {minus}9}cm{sup 3}s{sup {minus}1} of carriers to their opposite tail states. Their C{sub t} is close to the value (5{+-}2) {times} 10{sup {minus}9}cm{sup 3}s{sup {minus}1} obtained from optical measurements but higher than (0.5{+-}0.1) {times} 10{sup {minus}9}cm{sup 3}s{sup {minus}1} determined from photoelectric studies. Below T = 150K their model calculations overestimate {sigma}{sub p} because the tunneling transitions, becoming important for recombination and conduction, are neglected.
OSTI ID:
527714
Report Number(s):
CONF-960401--; ISBN 1-55899-323-1
Country of Publication:
United States
Language:
English