Characterization of an AlN buffer layer and a thick-GaN layer grown on sapphire substrate by MOCVD

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Corekci S., Ozturk M. K., Bengi A., Çakmak M., Ozcelik S., Ozbay E.

Journal of Materials Science, vol.46, pp.1606-1612, 2011 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 46
  • Publication Date: 2011
  • Doi Number: 10.1007/s10853-010-4973-7
  • Journal Name: Journal of Materials Science
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1606-1612
  • Gazi University Affiliated: Yes


An AlN buffer layer and a thick-GaN layer for high-electron-mobility transistors (HEMTs) were grown on sapphire substrate by metal-organic chemical vapor deposition (MOCVD). The structural and morphological properties of the layers were investigated by high resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM) techniques. The optical quality of the thick-GaN layer was also evaluated in detail by a photoluminescence (PL) measurement. It was found that the AlN buffer layer possesses high crystal quality and an atomically flat surface with a root-mean-square (rms) roughness of 0.16 nm. The screw-and edge-type dislocation densities of the thick-GaN layer were determined as 5.4 9 107 and 5.0 9 109 cm-2 by means of the mosaic crystal model, respectively. It was observed that the GaN layer has a smooth surface with an rms of 0.84 nm. Furthermore, the dark spot density of the GaN surface was estimated as 6.5 9 108 cm-2 over a scan area of 4 μm2. © Springer Science+Business Media, LLC 2010.