Results of measurement of d.c. electrical conductivity σ from 85 to 550 K are reported for eleven glass compositions of the Cd-Ge-As system. Three regions are seen in theσ-T data of all these glasses. In region I (85 to 140 K),σ is essentially constant and independent of temperature. In region II (200 to 430 K),σ is thermally activated with a single activation energy. In region III (>430 K) a sudden increase is seen inσ with temperature. From an analysis of the results, it has been possible to identify the mechanism of hopping conductivity among localised ‘defect’ states with region I, normal band type conductivity due to carriers excited to the extended states with region II and thermally assisted memory switching with region III.
In the composition dependence ofσ and ΔE for the CdGexAs2 glasses, special features are seen at the composition Cd28·57 Ge14·28 As57·15, which has equal mol fractions of CdAs2 and CdGeAs2. For the Cd2Ge-As glasses also, a maximum in ΔE and a minimum inσ are seen at this composition.
Volume 42 | Issue 6
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