Browsing by Author "Demirel P."
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Item Open Access Experimental study of two-step growth of thin AlN film on 4H-SiC substrate by metalorganic chemical vapor deposition(2010) Yu H.; Ozturk, M.; Demirel P.; Cakmak H.; Buyuklimanli, T.; Ou W.; Özbay, EkmelWe report growth optimizations of the thin AlN film on (0001) 4H-SiC substrates by metalorganic chemical vapor deposition. The influence of growth conditions, such as growth temperature and the V/III molar ratio, on the material quality of AlN film is studied. The surface morphology and crystalline quality of the epitaxial layers are investigated by atomic force microscope, X-ray diffraction, and transmission electronic microscope. A new approach is demonstrated to improve the crystalline quality of a 100 nm-thick AlN film by the use of a 5 nm-thick low temperature AlN nucleation layer. Compared to a conventional AlN layer directly grown on SiC substrate at high temperature, the surface morphology of two-step AlN film is remarkably improved along with a decreasing of defect density, leading to the improvement of crystalline quality for the subsequently grown GaN layer. The mechanisms of crystalline quality improvement by use of a low temperature AlN nucleation layer are also investigated and discussed.Item Open Access Mosaic structure characterization of the AlInN layer grown on sapphire substrate(Hindawi Publishing Corporation, 2014) Arslan, E.; Demirel P.; Çakmak H.; Öztürk, M.K.; Özbay, EkmelThe 150 nm thick, (0001) orientated wurtzite-phase Al1-x InxN epitaxial layers were grown by metal organic chemical vapor deposition on GaN (2.3 μm) template/(0001) sapphire substrate. The indium (x) concentration of the Al1-x InxN epitaxial layers was changed as 0.04, 0.18, 0.20, 0.47, and 0.48. The Indium content (x), lattice parameters, and strain values in the AlInN layers were calculated from the reciprocal lattice mapping around symmetric (0002) and asymmetric (10-15) reflection of the AlInN and GaN layers. The mosaic structure characteristics of the AlInN layers, such as lateral and vertical coherence lengths, tilt and twist angle, heterogeneous strain, and dislocation densities (edge and screw type dislocations) of the AlInN epilayers, were investigated by using high-resolution X-ray diffraction measurements and with a combination of Williamson-Hall plot and the fitting of twist angles. Copyright © 2014 Engin Arslan et al.