Electrical properties of glassy As xGe 10Te 90− x alloys

Abstract

This paper analyses the electrical properties of glassy alloys of As x Ge 10Te 90− x , while reporting the conductivity and dielectric constant of As 5Ge 10Te 85 and As 15Ge 10Te 75 compositions in the temperature range 77–383 K and the frequency range from dc to 5 MHz. The dc conductivity has been shown to be of the form σ dc=σ0 1 exp(−δE 1/kT) + σ0 2 exp(−δE 2/kT The ratio σ 0 1 / σ 0 2 is of the order of 10 6. ΔE 1, the higher temperature activation energy, is dependent on the composition, while ΔE 2, the lower temperature activation energy, is less dependent on the composition. The dielectric constant has been found to be independent of temperature and frequency up to about 253 K. However, at higher temperatures, it becomes activated and proportional to log ω. Some common features of As x Ge 10Te 90− x are a kink in dc conductivity, a ω 0.8 relationship for ac conductivity, no evidence of variable-range hopping at low temperatures, field-dependent conductivity and memory switching. The data can be interpreted in terms of the dangling-bond theory of Mott and his collaborators. A high density of states of the order of 10 20eV −1 cm −3 near the Fermi level may be expected.