• GaN;
  • MOVPE;
  • semipolar;
  • dislocation;
  • SEM;
  • XRD;
  • cathodoluminescence


We have succeeded in growing flat semipolar {11-22} GaN layers on r -plane patterned sapphire substrates (r -PSSs). However, the obtained GaN layers still contain a dislocation density of more than 3 × 108/cm2 which degrades the device performance. Thus, it is important to reduce this dislocation density. To reduce the density of dislocations generated at the interface between GaN and sapphire, we employed a shallowly etched r -PSS by reducing the selective growth area. However, it was difficult to grow a flat {11-22} GaN layer on the shallowly etched r -PSS owing to the low growth selectivity. Therefore, we used a two-step process, where growth temperature is changed during the growth. Consequently, we succeeded in obtaining {11-22} GaN on the shallowly etched r -PSS. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)