Coalescence of GaN nanopillars grown by Nano-Pendeo Epitaxy

An original method of compliant epitaxy, known as Nano-Pendeo Epitaxy, has been developed for achieving low dislocation density GaN and managing the strain into the nitride layers. Initial thin AlN and GaN layers are grown on silicon on insulator (SOI) layers, before being patterned into nanopillars. The degrees of freedom in rotation acquired by the nano-pillars allows the crystallites to align crystallographically at the time of coalescence, therefore without creating defects. This alignment is explained by a reduction of interface energy between adjacent crystallites slightly misorientated before coalescence. To go further quantitatively in the understanding of the crystallite alignment mechanisms at work and feed our numerical simulations, we would like to follow before and after coalescence of the nano-pyramids, the average evolution of the mosaicity and twist within a vignette of nano-pillars.