Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 57: Focussed Session: ZnO-based Semiconductors
HL 57.9: Vortrag
Donnerstag, 25. März 2010, 16:45–17:00, H17
Growth and Characterization of Hetero- and Homoepitaxial ZnO/ZnMgO Quantum Wells. — •Bernhard Laumer1, Thomas A. Wassner1, Fabian Schuster1, Martin Stutzmann1, and Martin Eickhoff2 — 1Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching — 2I. Physikalisches Institut, Justus-Liebig-Universität, Heinrich-Buff-Ring 16, 35392 Gießen
In this study, ZnO/Zn1−xMgxO single quantum wells (SQW) with different well widths have been grown by plasma-assisted molecular beam epitaxy on c-plane sapphire as well as on c-plane (O-face) bulk ZnO crystals. For heteroepitaxy on c-plane sapphire, a MgO/ZnO double buffer has been introduced to overcome the large lattice mismatch. Reflection high energy electron diffraction was used for in-situ growth monitoring and atomic force microscopy for ex-situ investigation of the sample morphology. The rms roughness of both hetero- and homoepitaxial SQW samples ranges from 0.2 to 0.4 nm, indicating the presence of well-defined and abrupt heterointerfaces. The optical properties of the quantum well structures were investigated by photoluminescence spectroscopy (PL). At 4.2 K, excitonic emission from the SQW is observed, that blue shifts for decreasing well width due to enhanced quantum confinement. As shown by temperature-dependent PL measurements, this emission line can be attributed to excitons localized at potential fluctuations of the SQW due to fluctuations of the barrier height or well width. At higher temperatures a second peak emerges that is attributed to free excitons.