The influence of sapphire substrate orientation on crystalline quality of GaN films grown by hydride vapor phase epitaxy

• Published in: Physica. B, Condensed matter Condensed matter, 2009-12, Vol.404 (23-24), p.4919-4921
• Main Authors: Govorkov, Anatolij, Donskov, Alexsandr, Diakonov, Lev, Kozlova, Yulia, Malahov, Sergej, Markov, Alexsandr, Mezhennyi, Mikhail, Pavlov, Vladimir, Polykov, Alexsandr, Yugova, Tatiana
• Format: Article
• Language: English
• Subjects: Hydride vapor phase epitatial; Nitride gallium; Structure
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2009.08.211

GaN films were grown by hydride vapor phase epitaxy on sapphire substrates with orientations c-(0001), a-(112¯0), m-(101¯0) and r-(101¯2) using N2 as a carrier gas. The crystalline perfection of the grown films was studied by X-ray diffraction, by optical microscopy and scanning electron microscopy and by microcathodoluminescence (MCL). It was found that, for c- and a-oriented sapphire substrates, the GaN films showed (0001) orientation, for m-oriented sapphire the films showed semi-polar (101¯3) orientation, while for r-sapphire substrates GaN layers with non-polar a(112¯0) orientation could be grown. The surface morphology of the GaN films and their crystalline structure strongly depended on the substrate orientation. With increasing the layer thickness the halfwidth of the X-ray rocking curves monotonically decreased which points to improvement of the crystalline quality. The best quality films were grown for the c- and r-oriented substrates: respectively, 460arcseconds at the thickness of 400mm, 600arcseconds at the thickness of 300μm. For m-oriented substrates the halfwidth was 1300arcseconds at comparable thickness. The density of stacking faults for semi-polar and non-polar films was determined by MCL imaging. The linear density of stacking faults was found to be 5×104cm−1 for films grown on m-oriented sapphire substrates and 5103cm−1 for a-GaN films grown on r-sapphire.