Electrical response of materials with recombining space charge

The small-signal transient and sinusoidal steady-state responses of a material with generation and recombination (G/R) of charge are considered. Immobile positive charge and mobile negative charge arise from the dissociation of intrinsic or donor centres and recombine bimolecularly. The mobile charge may react at electrodes. An exact solution for the steady-state admittance of the system is presented, along with exact and approximate equivalent circuits. The simple approximate circuits, made up entirely of frequency-independent elements are found to approximate the exact admittance to better than 1% for all frequencies and for realistic G/R conditions in the completely blocking situation. Similar accuracy is obtained for partly blocking conditions provided G/R and electrode reaction time constants are well separated.