Theory of photoionization cross sections of impurities in semiconductors

Previous approaches to the calculation of photoionization cross sections are reviewed and found to be inadequate. New calculations are presented which, for the first time, take into account the details of the valence bands and make use of Bloch functions for band states. The localized wavefunctions are chosen to satisfy symmetry requirements, and are then determined by reproducing experimental data. The method proves successful for a variety of shallow and deep impurities. (author)