Electronic structures of impurities and point defects in semiconductors

A brief history of the impurity theories in semiconductors is provided. A bound exciton model is proposed for both donor- and acceptor-like impurities and point defects, which offers a unified understanding for "shallow" and "deep" impurities and point defects. The underlying physics of computational results using different density-functional theory-based approaches are discussed and interpreted in the framework of the bound exciton model.