AC conductivity of amorphous semiconductors

Abstract

The models for dielectric relaxation which confine to well defined dielectric loss peaks suggested by the workers from dielectric school and that of frequency dependent ac conductivity suggested by the workers from semiconductor school are briefly reviewed. A brief description of the spurious effects which can give similar relaxation behaviour are also presented. Attempt has been made to explain the observed frequency and temperature dependence of ac conductivity in transition metal ion phosphate glasses by assuming two mechanisms. The first mechanism is responsible for well defined but broad dielectric loss peaks and dominate in the region where measured ac conductivity approaches dc conductivity. Such a mechanism can give a slope of 0·5 over several decades of frequency even in the region where measured ac conductivity is substantially higher than dc conductivity. The second mechanism is responsible for almost linear or sublinear frequency dependent ac conductivity and dominates in the temperature and frequency region where measured ac conductivity is substantially higher than dc conductivity. Measurements of dielectric constant in other amorphous systems in the region where measured ac conductivity approaches dc conductivity are needed to check the validity of the model and the exact origin of the two mechanisms of ac conductivity.