The optical properties of various structural models for amorphous and hydrogenated amorphous material were studied with regard to the manner in which topological disorder, H content, and various types of defect (dangling bonds, floating bonds) influenced the shape of the optical absorption spectrum and the position of the Urbach edge. The absorption behavior was characterized by the joint density of states. The overall structure of the optical absorption spectrum was determined mainly by the degree of topological disorder and the amount of H. The presence of defects gave rise to tail absorption. Dangling bonds affected the optical properties more than did floating bonds.

Disorder, Defects, and Optical Absorption in a-Si and a-Si:H S.Knief, W.Von Niessen: Physical Review B, 1999, 59[20], 12940-6