Dresden 2009 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 14: Photonic Dielectrics III

DF 14.2: Talk

Thursday, March 26, 2009, 10:40–11:00, WIL A317

Theoretical discussion of present and novel optical methods for space-charge wave analysis — •Kay-Michael Voit, Burghard Hilling, and Mirco Imlau — Department of Physics, University of Osnabrück, Osnabrück, Germany

Space-charge waves are commonly generated in semi-insulating materials via exposure to an oscillating sinusoidal light interference pattern under an application of high electric fields. However, both the study of nonlinear mutual interactions of SCWs and the investigations of charge-transport properties by SCW spectroscopy are restricted by the assumptions underlying the theoretical concept for SCW analysis: (1) the oscillation amplidudes should be smaller than unity so that the oscillating fringe pattern can be separated into a static and two counterpropagating running gratings and, (2) the modulation depth of the fringe pattern should be smaller than unity. Furthermore, the analysis does not allow to determine the sign of the involved charge carriers. Hence it was the aim of our theoretical and experimental study to develop a new technique which overcomes these restrictions. In this contribution, the assumptions made for the analysis of the oscillating technique are presented and discussed with respect to the experimental restrictions. The novel approach of SCW generation by simultaneous exposure with a static and a running fringe pattern having the same spatial frequency is developed starting from the Kiev equations. Key aspects of the derivation are presented and the formula are compared to the well-known equations for SCW generation with an oscillating fringe pattern.