Dresden 2009 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 2: Dielectric Spectroscopy & Microscopy

DF 2.1: Talk

Monday, March 23, 2009, 10:40–11:00, WIL A317

Space-charge wave spectroscopy of hexagonal silicon carbide — •Michaela Lemmer, Burkhard Hilling, and Mirco Imlau — Department of Physics, University of Osnabrück, Osnabrück, Germany

Space-charge wave (SCW) spectroscopy is based on resonant excitation of SCW in a semi-insulating material, for instance, high resistive semiconductors. This promising new technique allows to examine important photoelectric parameters of a wide variety of materials.
Here, hexagonal silicon carbide with 4H and 6H stacking sequence has been investigated by SCW spectroscopy. For SCW excitation, the sample is exposed to a light pattern oscillating around an equilibrium position. This is realized with a two-beam Mach-Zehnder interferometer, where one of the beams is sinusoidally phase-modulated with an electro-optic phase-modulator. The dispersion behaviours found for the 4H sample indicate the existence of trap recharging waves and yield the product of mobility and lifetime µ τ and the effective trap density N_eff. The data set of the 6H polytype indicates a comparably smaller effective trap density, but an unambiguous assignment to the existence of trap recharging waves fails. Taking into account the general classification of material parameters which provides the existence for SCW, the particular case of damped, forced charge-density oscillations can be concluded.
Financial support from the Deutsche Forschungsgemeinschaft (DFG, project Nos. GRK 695 ”nonlinearities of optical materials”) is gratefully acknowledged.