The properties of such defects, as revealed by optical and electron spin resonance spectroscopy, were reviewed. Particular attention was paid to the A-center, which was a complex that involved a cation vacancy and a shallow donor. Cation and anion vacancies were treated, but information concerning interstitials was scarce. Some older data were reinterpreted. Although the amount of reliable information was small, it was sufficient to permit tentative general concepts to be advanced.

J.W.Allen: Semiconductor Science and Technology, 1995, 10[8], 1049-64