Theory of the thermally-stimulated-current transport peak. Application to a dispersive transport case

Thermally-stimulated-current (TSC} technique consists of heating a dielectric, with excess carriers having been introduced. The current flowing under the effect of applied electric field is then recorded as a function of increasing temperature. The current maximum obtained is called a "transport TSC peak" if it appears due to thermally activated transport of carriers initially generated at one electrode and collected at the other. In this paper the transport of carriers, controlled by multiple trapping, is studied when the temperature of the system is increased linearly with time. The general equations for current density in a TSC experiment are obtained and are applied for the cases of a single trap and an exponential trap distribution. The condition for a TSC current maximum, initial rise of current, and partial heating technique are studied in detail. The properties of the transport TSC peak differ considerably from those of the classical TSC; the position of the current maximum and activation energy found from partial heating at the maximum depend on the field applied and on sample thickness, It is also found that there exists a correlation between the transport TSC peak and time-of-flight signal, and the transport parameters found from TSC (activation energy of mobility, parameter of dispersion a, etc.) correspond to those of the time of flight measurements. The critical trap criterion and concepts of lifetime and transit time are extended to the general case of nonisothermal transport.