Dresden 2009 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 40: ZnO: preparation and characterization III

HL 40.9: Vortrag

Donnerstag, 26. März 2009, 12:00–12:15, BEY 118

Influence of uniaxial strain onto the optical and vibrational properties of high quality ZnO substrates — •Gordon Callsen, Markus R. Wagner, Ronny Kirste, Jan Schulze, and Axel Hoffmann — Technische Universität Berlin, Department of solid state physics, Hardenbergstr. 36, 10623 Berlin, Germany

Homoepitaxial growth of ZnO films requires high quality ZnO substrates with minimal strain and a low impurity concentration. Justified by these requirements we evaluate ZnO substrates of several main suppliers. Therefore, we apply Micro-Raman, XRD and uniaxial strain depended PL measurements. XRD measurements clearly show that the c/a ratio is not a constant throughout the selection of our samples. This is mainly due to a varying compressive strain and defects in the samples as revealed by Micro-Raman measurements. In order to gain further insight into these results we investigate the influence of uniaxial strain onto the free and bound excitonic emission lines of the ZnO substrates (PRB 56, 13087). The uniaxial strain induced change of the crystal field causes a shift of the free excitonic lines. This allows the determination of the deformation potentials of the ZnO substrates (JJAP 40, L1089). The results of those measurements give further insight into the symmetry and ordering of the ZnO valence band. The controlled change of the piezo-electric field of the ZnO crystal also provides conclusions concerning the pressure induced shift of the bound excitons with their different localization energies. Based on our evaluation of the ZnO samples we map out necessary requirements for ZnO substrates in order to achieve homoepitaxial growth of ZnO.