On the theory of the deep levels of transition metal impurities in semiconductors

The scattering of band electrons accompanied by the excitation of an unfilled d shell of an impurity atom is considered to be the origin of the deep levels associated with transition-metal impurities in semiconductors. In order to describe the energy states of the system, the Anderson model, generalized for the case of the electron spectrum with the gap, is used. The activation-energy dependence of the parameters of the model is found. It is shown that this mechanism is able to explain the existence of deep levels with symmetries which coincide with that of an unfilled impurity shell.