Drift mobility studies in vitreous arsenic triselenide

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Abstract
The drift of charge carriers in thin vitreous films of arsenic triselenide has been examined by a transit time technique. The specimens used were prepared by cooling from the molten state, rather than by evaporation. Electron mobility measurements were found to be impractical, the mobility being estimated as less than 10−10 m2 v−1 sec−1 at room temperature. The hole mobility was measurable, however, and was found to be strongly dependent on temperature and applied electric field. The hole transit pulses were of a ‘rounded’ form, indicating a spread of carrier transit times. The field dependence was of a form attributable to the Poole–Frenkel effect (field-stimulated emission of carriers from charged trapping centres). After extrapolation of the measurements to zero applied field, the temperature dependence of the mobility indicated an activation energy of about 0·43 ev. These results, and those of a subsidiary examination of the temperature and field dependence of the specimen conductivity, are discussed in terms of the band structure of the material. A possible cause of the transit pulse rounding is also advanced. Finally, an account is given of the observation of bistable switching action in the specimens.