K-map study of the coalescence of optimized GaN nanopillars grown by Nano-Pendeo Epitaxy

An original method, known as Nano-Pendeo Epitaxy, has been developed for achieving low threading dislocation density (TDD) gallium nitride (GaN). It is based on the self-realignment of GaN on Si(111) nano-pillars. This study has two goals. Firstly, to understand the coalescence mechanisms. Secondly, to construct a model to predict optimal structures for low TDD layers. Measurements performed on the ID01 beamline proved that it is possible to measure the change in lattice tilt of the GaN and silicon (Si) layers before and after coalescence which proved that the growth occurs as expected. Simpler samples are needed to better understand the growth process. Using an alternative sample, insight into pillar coalescence in lines was gained through dark field X-ray microscopy measurements on ID06, but the low intensity of thin Si layers prevented examination of Si behavior. Therefore, we aim to measure the tilt and strain distribution in the Si pillars and GaN layers within optimized samples.