High-field conduction and dielectric study in a-Se78−xTe22Bix alloys

The present paper reports the measurements on space charge limited conduction (SCLC) in vacuum evaporated amorphous thin films and dielectric relaxation study in bulk of Se78−xTe22Bix where 0⩽x⩽4. At high fields (∼104 V/cm), the current could be fitted to the theory of SCLC, in case of a uniform distribution of localized states in the mobility gap of these materials. The results indicate an increase in the density of localized states on addition of bismuth (Bi) in the Se78−xTe22Bix system. The value of density of the states N(EF) increases two orders of magnitude at x⩾2. The nature of the capacitances is also changes at x⩾2, i.e. from positive to negative capacitance. This transition at x⩾2 may be explained in terms of a change in conduction from p- to n-type, when the Bi concentration is increased.