Impurity states in narrow-gap and gapless semiconductors

The influence of interband interactions on the location of impurity stages in narrow-gap and gapless semiconductors of A^IVB^VI type is considered in the T-matrix approximation. It is shown that taking account of the interband interaction results in diminution of the activation energy of the impurity level.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 108–111, January, 1977.The authors are grateful to B. L. Gel'mont for discussing the research and the remarks made.