Time Dependence of Electronic Processes in Dielectrics

In solid dielectrics electrons may be excited from low levels into conduction levels or into traps with energies slightly lower (shallow traps) by an ionizing radiation or by the action of strong fields. It is assumed that collisions amongst electrons in these levels are so frequent that an electronic temperature T is established which may be different from the lattice temperatures. Also the number of electrons in these levels need not correspond to equilibrium at temperature T , in which case transitions to or from lower levels (of lattice defects or foreign admixtures) will take place. Such transitions are either due to excitation by sufficiently fast moving electrons in the conduction levels, or to the inverse process. In this way it is possible to account for recombination within a reasonable time provided these lower levels (denoted as deep traps) are not much more than 1 electron volt below the lowest of the shallow traps. The difficulty of having to introduce recombination with simultaneous emission of very many vibrational quanta, an extremely unlikely process, is thus avoided. Other applications of this method, for example to the time dependence of electronic conductivity in strong fields, are indicated.