Berlin 2008 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 14: Electric, electromechanical and optical properties II
DF 14.4: Vortrag
Donnerstag, 28. Februar 2008, 15:00–15:20, EB 407
Space-charge waves of the low-frequency branch with a linear dispersion law — •Michaela Lemmer1, Mirco Imlau1, Manfred Wöhlecke1, Mikhail P Petrov2, and Konstantin Shcherbin3 — 1Department of Physics, University of Osnabrück, Osnabrück, Germany — 2Ioffe Physico Technical Institute, St. Petersburg, Russia — 3Institute of Physics, National Academy of Sciences, Kiev, Ukraine
ac and dc currents arising in CdTe:Ge during optical
excitation of space-charge waves (SCW) have been investigated. The experiments have been performed at a wavelength of λ = 1064 nm using the technique of an oscillating interference pattern. Our investigations have shown that the SCW studied can be attributed unambiguously to trap recharging waves (TRW). Remarkably, we have found a linear dispersion law (ΩK ∼ K) for these waves although an inverse law is usually expected. A corresponding theoretical model has been developed and shows that the theoretical data are in reasonable agreement with the experiments if the following fitting parameters are used: An effective trap concentration of Neff = (2.5 ± 0.3) · 1012 cm−3, a mobility-lifetime product of µ τ = (0.65 ± 0.05) · 10−7 cm2/V, and a Maxwell relaxation time of τM = (5.5 ± 0.2) · 10−3 s. The appearance of an additional low-frequency ac resonance is discussed in the frame of a bipolar conductivity.
Financial support of the Deutsche Forschungsgemeinschaft (DFG, projects GRK 695 and RUS 17/15/07) is gratefully acknowledged.