The current saturation associated with the acoustoelectric effect has been investigated in photoconducting crystals of cadmium sulphide. Under normal band gap irradiation the current-voltage characteristic measured under pulsed conditions shows a departure from Ohm's law at a critical field, E(_c), of the order of l0(^3)v cm(^-1). The current saturation is associated with the internal generation of acoustic flux which occurs when the electron drift velocity, v(_d), exceeds the velocity of sound, v(_s), in the crystal. In consequence the critical field for saturation is determined by the drift mobility µ(_d) = v(_s) /E(_c). The work described in this thesis concerns the measurement of the drift mobility and its relationship to the experimentally determined Hall mobility, fd^, as a function of conductivity and temperature. In uniform samples the critical field at room temperature was independent of conductivity over the range 10(^-4) to 10(^-2) ohm(^-1)cm(^-1). The corresponding values of µ(_d)were all about 300 cm(^2)v(^-1)sec(^-1) in most of the samples studied and agreed well with the measured values of the Hall mobility. With non-uniform samples, however, the critical field varied strongly with the intensity of incident illumination. Under saturated conditions potential probe measurements on uniform samples revealed the presence of a stationary high field domain near the positive electrode.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:585938 |
| Date | January 1970 |
| Creators | Islam, M. N. |
| Publisher | Durham University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.dur.ac.uk/8698/ |
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