Growth and coalescence behavior of semipolar (11(2)over-bar2) GaN on pre-structured r-plane sapphire substrates

Semipolar (11 (2) over bar2) oriented GaN has been grown on a pre-structured r-plane sapphire substrate. By using silicon doped marker layers (MLs) we have been able to monitor the growth evolution of the stripes until coalescence. With that technique we correlated the growth type (direction) with the results of cathodoluminescence (CL) and transmission electron microscopy. Both characterization methods show only a few defects for the major part of the structure and a relatively high defect density for material grown in a-direction at one side of the stripes. It is shown that during coalescence these defects are mainly terminated resulting in a flat, planar (11 (2) over bar2) GaN layer with strongly reduced defect density. Additionally, X-ray diffraction (XRD) measurements show the high quality of these layers. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim