URBACH EDGE OF CRYSTALLINE AND AMORPHOUS-SILICON - A PERSONAL REVIEW

The availability of high quality wafers and films, the extensive literature on their optical, electrical and microscopic properties, and the wide spread interest in their applications suggests that a comparison of the absorption edge of c-Si and a-Si:H can be uniquely rewarding. This paper is a personal review of the experimental Urbach edge phenomena for c-Si and a-Si:H to highlight differences and similarities on the basis of simple physical models and a recent first principles theory of the energy, temperature, and static disorder dependence of the optical absorption edge.