Study by nano-XRD of the coalescence of GaN nanopillars grown by Nano-Pendeo Epitaxy

An original method has been developed for achieving low dislocation density gallium nitride (GaN) and managing the strain in the nitride layers. It is based on the self-realignment of Si(111) nano-pillars (NP) during nitride layer coalescence. This study has several goals: (i) determine the degree of tilt and twist of the individual Si NP induced by coalescence; (ii) obtain the in-plane and out-of-plane strain distribution for the GaN layer, which will give us further information about the threading dislocation density (TDD) in our platelets. We will study the coalescence process with the variation of the pitch (center-to-center distance) by testing samples with varied pitches but the same NP diameter. We also intend to study the layers for various GaN growth times in order to better comprehend each step of the GaN pyramid coalescence. These observations will provide a clear picture of the coalescence process which will be beneficial to grow GaN platelets with low TDD.