Dielectric Spectroscopy of Semiconductors: Interpretation of the Frequency Response of Trapping Processes in Semiconductors.
Progress rept. no. 2,
ROYAL HOLLOWAY AND BEDFORD NEW COLL EGHAM (ENGLAND)
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The frequency dependence of trapping processes measured by the technique of Dielectric Spectroscopy of Semiconductors DSS reveals a ubiquitous and not generally recognized tendency to the universal fractional power laws, in complete contrast with Debye-like responses which would correspond to the normally expected exponential dependence on time. There is at present no accepted theory to account for this. We propose that one explanation may be found in a modification of our earlier model of screened hopping in which the presence of a localized electron at a trapping site affects the energy of that site through a screening process by a re-adjustment of the occupancy of other neigbouring sites. The screeningg determines the loss, while the transverse displacement of the electrons determines the polarization. Depending on the relative importance of these two processes, the exponent of the fractional power law may vary between almost zero, corresponding to very-low-loss frequency-independent behaviour at low frequencies, the so-called Low Frequency Dispersion LFD, on the other. Electrochemical reactions may also play a role in certain interfacial processes. Great Britain.
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