The interaction between light and electrons in semiconductors forms the basis for many interesting and practically significant properties. This book examines the fundamental physics underlying this rich complexity of photoelectronic properties of semiconductors and will familiarise the reader with the relatively simple models that are useful in describing these fundamentals. The basic physics is also illustrated with typical recent examples of experimental data and observations. Following introductory material on the basic concepts, the book moves on to consider a wide range of phenomena, including photoconductivity, recombination effects, photoelectronic methods of defect analysis, photo effects at grain boundaries, amorphous semiconductors, photovoltaic effects and photo effects in quantum wells and superlattices. The author is Professor of Materials Science and Electrical Engineering at Stanford University and has taught this material for many years. He is an experienced author, his earlier books have found wide acceptance and use. Readers will, therefore, find this volume to be an up-to-date and concise summary of the major concepts, models and results. It is intended as a text for graduate students but will be an important resource for anyone researching in this interesting field.