Reduction of threading dislocation density in top-down fabricated GaN nanocolumns via their lateral overgrowth by MOCVD
Vitaly Z. Zubialevich, Mathew McLaren, Pietro Pampili, John Shen, Miryam Arredondo, P. J. Parbrook
Abstract
Reduction of threading dislocation density in top-down fabricated GaN nanocolumns (NCs) via their successive lateral shrinkage by anisotropic wet etch and lateral overgrowth by metalorganic chemical vapor deposition is studied by transmission electron microscopy. The fabrication process involves a combination of dry and wet etches to produce NC arrays of a low fill factor (<5%), which are then annealed and laterally overgrown to increase the array fill factor to around 20%–30%. The resulting NC arrays show a reduction in threading dislocation density of at least 25 times, allowing for the reduction in material volume due to the array fill factor, with dislocations being observed to bend into the voids between NCs during the overgrowth process.