Electrical transport in chalcogenide (Se-Te-As-Ge) glasses

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Abstract
Varying degrees of curvature were found in all plots of log conductivity and thermoelectric power against I|T. The data are examined in the light of the current theories, and are best fitted to the parallel conduction model in the extended and the localized edge valence states proposed by Xagels, Callaerts and Denayer (1974). Although the theoretical fits to the experimental data were satisfactory, the 300 K effective densities of states, Nv and NB, at the mobility edge and the localized band edge were found to be about 2.2 × 1019 and 1.8 × 1021 cm−3, respectively, with a localized bandiail depth of ∼ 0.1 eV. It is argued that such a large NB is physically unrealistic. Considering variable-range hopping in the localized states as suggested by Grant and Davis (1974), reduces NB to about 6.8 × 1020 cm−3 at 300 K by assuming a hopping distance of 20 Å and a localization parameter of 0.1 Å−1.