Internal Field-Assisted Thermal Ionization

The bulk-limited electronic transport due to field-assisted thermal ionization of coulomb trapping centers is considered, taking into account the internal electric field contribution. Previous theories of the effect are presented and compared with the present model which is in agreement with the experimental electrical current characteristics obtained over a wide range of temperature and applied field in several differently doped CdF2 crystals and in SiO films. Possible origins of the internal electric field are discussed and a theoretical evaluation based on the electron-phonon interaction is given.