Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 48: ZnO: Devices

HL 48.5: Talk

Wednesday, March 16, 2011, 11:15–11:30, POT 151

Excitonic Transport in a ZnMgO/ZnO Quantumwell — •Martin Noltemeyer¹, Thomas Hempel¹, Jürgen Christen¹, Matthias Brandt², Michael Lorenz², Marius Grundmann², Andrey Polyakov³, and Mikhail Stepovich³ — ¹Institute of Experimental Physics, Otto-von-Guericke-Universität Magdeburg — ²Institut fuer Experimentelle Physik II, Universität Leipzig — ³Tsiolkovsky Kaluga State University, Russia

Using highly spectrally and ps-time resolved cathodoluminescence (CL) the excitonic transport in a c-oriented PLD grown ZnMgO/ZnO quantumwell (QW) of about b=4nm thickness is indirectly measured as a function of temperature (T=5K-180K). In a first step, the initial exciton lifetime τ of the QW (E_QW(5K)=3.22eV) is assigned by time resolved CL on the uncovered sample area. It decreases over one order of magnitude from τ(5K)=3.75ns to τ(180K)=0.38ns. In a second step, the sample is excited by the pulsed e-beam in the center of a circular aperture (d=1.45µm) in a completely light absorbing Ti-mask (thickness: 160nm). The analytic solution of the two-dimensional diffusion equation for this geometry is fitted to the initial decay of the CL with the given parameters τ(T) and d(T). This directly gives the diffusion constant D(T) which increases from D(5K)=0.25 cm²/s to D(180K)=1.4 cm²/s. Using the Einstein-Relation, one can define an excitonic mobility that has a plateau around µ=600 cm²/Vs at low T (5K-12K) with a decay at higher temperature following µ∝T^−2/3 which is close to scattering with Fröhlich-Interaction (µ∝T^−1/2).