Berlin 2008 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 14: Electric, electromechanical and optical properties II

DF 14.4: Talk

Thursday, February 28, 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 (Ω_K ∼ 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 N_eff = (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 τ_M = (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.