Migration of electrons via triple-charged defects of crystal matrix

Abstract

The study of semiconductor materials with point radiation defects of the crystal structure in three charge states (–1), (0), (+1) is important for determining the conditions of their radiation resistance under the influence of gamma rays, fast electrons, etc. Such defects are self-sufficient to ensure electrical neutrality of the material under conditions of ionization equilibrium, that issue determines the radiation resistance of materials. In silicon and diamond crystals, such irradiation-induced defects during their accumulation stabilize the Fermi level in the vicinity of one third of the band gap from the top of the valence band. The purpose of the work is an analytical description of the stationary hopping electron transfer in a semiconductor, taking into account the joint migration of both the single electrons and the pairs of electrons over these triple-charged defects. A crystalline semiconductor is considered as a matrix containing immobile point defects of one sort in the prevailing concentration. For the first time in the drift-diffusion approximation, a phenomenological theory is constructed of coexisting migration of both the single electrons (transitions from the charge state (–1) to state (0) and from the state (0) to state (+1)), and the electron pairs (transitions from the state (–1) to state (+1)) by means of their hopping between such defects when an external stationary electric field is applied to the semiconductor. In the linear approximation, analytical expressions are obtained for the screening length of a static electric field and the length of the hopping diffusion of electrons migrating via such defects. It is shown that the additional contribution of the hopping transport of electron pairs leads to a decrease in the screening length and also changes the diffusion length.