Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 39: ZnO and Relatives II

HL 39.3: Talk

Tuesday, March 27, 2012, 12:00–12:15, EW 202

Temperature dependent properties of ZnO/(Mg,Zn)O quantum wells with and without a distinct QCSE — •Marko Stölzel, Johannes Kupper, Matthias Brandt, Alexander Müller, Gabriele Benndorf, Michael Lorenz, and Marius Grundmann — Institut für Experimentelle Physik II, Universität Leipzig, Linnéstr. 5, 04103 Leipzig, Germany

Confinement effects, the Stokes shift and the quantum-confined Stark effect (QCSE) determine the luminescence properties of polar ZnO/(Mg,Zn)O quantum wells (QWs). We present temperature dependent photoluminescence and optical transmission measurements to separate these effects and determine the origin of the luminescence.

Single QW structures have been prepared by pulsed laser deposition (PLD) on a-plane sapphire substrate exhibiting excitons with and without a distinct QCSE. The QCSE leads to a redshift of the QW luminescence maximum beneath the free exciton energy in ZnO as well as a change of the dynamics from a single exponential decay function to a non-exponential one, well described by a stretched exponential decay function. The internal electric field was evaluated to 0.66 MV/cm. Based on QWs without a distinct QCSE, the Stokes shift will be determined in dependence of well width and temperature.

The radiative decay time was found to increase linearly with temperature for both types of QWs indicating free exciton emission as the major recombination channel. With increasing temperature, the internal electric field is screened by free charge carriers, leading to a drop of the radiative decay time and reduction of the redshift above 50 K.