Crystal orientation of GaN layers on (10(1)over-bar0) m-plane sapphire

Based on the atomic arrangement of the (10 (1) over bar0) m-plane sapphire surface, we have developed a model for the initial nucleation process of gallium-nitride (GaN). This model describes why (11 (2) over bar2) and (10 (1) over bar(3) over bar) are the preferred orientations of GaN on the (10 (1) over bar0) sapphire. The experimental results from high-resolution X-ray diffraction measurements, like the crystallographic relations and the twinning of the (1 (1) over bar0 (3) over bar) orientation are explained by the model too. Our model also predicts that (11 (2$) over bar2) thin films are metal-polar and (1 (1) over bar0 (3) over bar) thin films are nitrogen-polar. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim