Influence of carrier diffusion on transient one-carrier injection current in an insulator with traps

The main influence on the transient process is shown to be exerted by the initial trapped space charge entering the dielectric before the onset of injection by carrier diffusion. This charge leads to a sharp decrease of the transient current and to a superlinear dependence of its value on the applied voltage in comparison with the case without diffusion. Approximate analytical solutions for the initial charge distribution and the transient current behavior are derived. They correspond to the results of an exact (numerical) solution of the general problem. Criteria for the validity of the diffusionless approximation are found.