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HL: Fachverband Halbleiterphysik

HL 46: Poster 2

HL 46.51: Poster

Donnerstag, 29. März 2007, 15:00–17:30, Poster A

Electrical Properties of Low Temperature ZnO Layers Grown by MOVPE on GaN/Sapphire Templates — H. Witte, S. Tiefenau, A. Krtschil, •S. Heinze, A. Dadgar, and A. Krost — Institute of Experimental Physics,Otto-von-Guericke-University-Magdeburg, 39016 Magdeburg

High-quality ZnO layers grown by metal-organic vapor phase epitaxy on GaN/sapphire templates typically use a low temperature (LT)-ZnO buffer layer grown at 450 ⁰C to reduce the lattice mismatch. In general, the LT-ZnO shows high n-type conductivity properties with a donor concentration gradient from the GaN/LT-ZnO interface towards the surface as obtained from differences between the electron concentrations and the net donor concentrations measured by Hall-effect and by CV-characteristic, respectively. In internal photo-voltage spectra signals from near-band-gap (NBG) transitions in GaN as well as in ZnO were observed. These defect-to-band-transitions suggest an accumulation of ZnO- related defects with E_G- 0.03 eV, - 0.11 eV and - 0.2 eV in the near of the GaN/LT-ZnO-interface. They decrease after annealing of the samples at 900 ⁰C for some minutes and by growing high temperature (HT) ZnO layers on the LT-ZnO buffer. Otherwise, the electron concentrations and the net donor concentrations of these LT-ZnO layers increase. In photo-current and photo-voltage spectra the defect-transition at E_G-0.11 eV dominates in samples annealed above 850 ⁰C. Furthermore, intensive illumination of LT-ZnO layers decrease temporary the electron concentration drastically. This annealing behaviour of LT-ZnO is contrary to those of the HT-ZnO.