On defining the optical gap of an amorphous semiconductor: an empirical calibration for the case of hydrogenated amorphous silicon

It is pointed out that there are a number of different means whereby the op tical gap of an amorphous semiconductor may be defined. We analyze some hyd rogenated amorphous silicon data with respect to a number of these empirica l measures for the optical gap. By plotting these gap measures as a functio n of the breadth of the optical absorption tail, we provide a means of rela ting these disparate measures of the optical gap. (C) 1999 Elsevier Science Ltd. All rights reserved.