Disorder, defects, and optical absorption in a-Si and a-Si : H

In this paper we present the optical properties of various structural model s for a-Si and a-Si:H. We discuss how topological disorder, hydrogen conten t, and different types of defects (dangling bonds and floating bonds) influ ence the shape of the optical-absorption spectrum and the position of the U rbach edge. The absorption behavior is characterized by the joint density o f states. The band gaps are obtained via the Tauc plot. The principal struc ture of the optical absorption spectrum is determined mainly by the degree of topological disorder and the amount of hydrogen. The presence of defects gives rise to tail absorption. Dangling bonds affect the optical propertie s more than floating bonds do. [S0163-1829(99)08319-8].