Improvements in a-plane GaN crystal quality by AlN/AlGaN superlattices layers

Abstract Non-polar (1 1 2¯ 0) a -plane GaN films have been grown by low-pressure metal-organic vapor deposition on r -plane (1 1¯ 0 2) sapphire substrate. We report on an approach of using AlN/AlGaN superlattices (SLs) for crystal quality improvement of a -plane GaN on r -plane sapphire. Using X-ray diffraction and atomic force microscopy measurements, we show that the insertion of AlN/AlGaN SLs improves crystal quality, reduces surface roughness effectively and eliminates triangular pits on the surface completely.