Suleyman Ozcelik

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We report the remarkably improved crystal quality of semi-insulating GaN grown by metalorganic chemical vapor deposition on an AlN buffer layer, which is deposited on sapphire substrate. The electrical and structural properties are characterized by dark current–voltage transmission line model and X-ray diffraction measurements. It is found that the crystal(More)
In the present study, we reported the results of the investigation of electrical and optical measurements in AlxGa1−xN /GaN heterostructures x=0.20 that were grown by way of metal-organic chemical vapor deposition on sapphire and SiC substrates with the same buffer structures and similar conditions. We investigated the substrate material effects on the(More)
Hall effect measurements on undoped Al0.25Ga0.75N/GaN heterostructures grown by a metalorganic chemical vapour deposition (MOCVD) technique have been carried out as a function of temperature (20–350 K) and magnetic field (0–1.5 T). Magnetic field dependent Hall data were analysed using the quantitative mobility spectrum analysis (QMSA) technique. The(More)
related parameters extracted by simple parallel conduction extraction method S. B. Lisesivdin, A. Yildiz, N. Balkan, M. Kasap, S. Ozcelik, and E. Ozbay Nanotechnology Research Center, Bilkent University, Bilkent, 06800 Ankara, Turkey Department of Physics, Faculty of Science and Arts, Gazi University, Teknikokullar, 06500 Ankara, Turkey Department of(More)
We present surface properties of buffer films (AIN and GaN) and Al0.3Gao.zN/Al2O3-High Electron Mobility Transistor (HEMT) structures with/without AIN interlayer grown on High Temperature (HT)-AIN buffer/Al2O3 substrate and Al2O3 substrate. We have found that the GaN surface morphology is step-flow in character and the density of dislocations was about(More)
Hall effect measurements on unintentionally doped Al0.25Ga0.75N/GaN/AlN heterostructures grown by metal organic chemical vapor deposition (MOCVD) were carried out as a function of temperature (20–300 K) and magnetic field (0–1.4 T). Magnetic-field-dependent Hall data are analyzed using the quantitative mobility spectrum analysis (QMSA) technique. The QMSA(More)
Hall effect measurements on undoped Al0.2Ga0.8N/AlN/GaN/AlN heterostructures grown on 6H-SiC substrates were carried out as a function of the temperature (30–300 K) and magnetic field (0–1.4 T). Measurements were carried out under dark and after-illumination conditions. After the dark measurements, the samples were illuminated with a blue light emitting(More)
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