Transient photocapacitance and photocurrent studies of undoped hydrogenated amorphous silicon

Abstract

We have applied transient photocapacitance and transient junction photocurrent measurements to the study of undoped hydrogenated amorphous silicon (a-Si:H) films, and find that the electronic optical transition from the dominant deep defect is very similar in energy to the D−→D0+e optical transition identified in n-type doped a:Si:H films. In addition, we have observed a competing hole thermal transition, and we have obtained estimates of its thermal emission rate and of the thermal gap. We have used the difference between photocapacitance and photocurrent in the valence-band tail region to determine the quantity (μτ)hNT at different temperatures. Finally, we have observed that light-induced metastable defects have a hole capture cross section significantly larger than that of the intrinsic defects.