Polarization effect of free carriers in ZnO single crystal

Considering the response of free charges to high frequency alternating current (AC) electric field and multi-emission and capture processes of weakly bound charges, dielectric relaxation effect of free carriers are proposed in this paper. According to this model, free charges and bound charges are regarded as the same except for the difference in transport distance, which is defined by the frequency of applied AC electric field. Therefore conduction process of free charges and dielectric relaxation process of weakly bound charges in traditional dielectric theories are believed in this new model to originate from the same micro-mechanism of charge transport. In order to verify the validity of this model, dielectric properties of ZnO single crystal were measured by Novocontrol wide band dielectric spectrometer in temperature range from -120 to 30°C and frequency range from 1 to 10⁷Hz. The relationship between electronic trap relaxation and dielectric relaxation effect of conduction process are discussed in detail. It was found that dielectric abnormity at low frequency and high frequency originates from conduction process of free carriers in grain and electronic trap relaxation at depletion layer respectively, both of which originate from the same micro-mechanism of electronic transport bound by intrinsic point defect. The paper offers a completely new way to understand and investigate dielectric relaxation phenomena.