Narrow Band-Gap a-Si:H with Improved Minority Carrier-Transport Prepared by Chemical Annealing

Abstract
A-Si:H films with narrow optical band gap down to 1.50 eV along with low hydrogen content down to 1 at% were fabricated using the concept of “chemical annealing”; alternating deposition with exposure to atomic hydrogen. Reduction in the density of the valence band tail states was confirmed by a time-of-flight experiment which exhibited non-dispersive behavior in the transient photocurrent curves and significant enhancement in drift mobility to 0.2 cm2/V·s at 300 K for holes. Remarkable improvement in the light induced metastability was also confirmed in some specimens annealed well, maintaining a photoconductivity 10-4 S/cm under AM1 white light illumination.