Excitons in Semiconductors

These lectures are intended to provide a coherent account of the fundamental properties of both free and bound excitons in semiconducting crystals. The emphasis is upon a description of those properties most relevant to the exploitation of exciton-related properties in the derivation of parameters of the semiconductor, both intrinsic and the extrinsic properties related to impurity and defect states, rather than the more formal treatment which is already provided in other chapters of this book. The discussions naturally centre on the optical properties, from which most aspects of the behaviour of excitons in semiconductors have been discovered and interpreted. Section I concerns the properties of free excitons, Section II contains the main characteristics of weakly bound excitons other than those related to satellite optical transitions, caused by phonon coupling and excited electronic states of the centre binding the exciton which are the subject of Section III. Special effects related to high excitation intensity are briefly reviewed in Section IV, other than electron-hole drops. The latter do not involve exciton states are are treated separately in this book.