Structure evolution of MOCVD regrown AlN on high temperature annealed AlN/Sapphire templates

Abstract In this work, systematic investigations of structural information towards metal-organic chemical vapor deposition (MOCVD) regrown AlN on high temperature annealed AlN template were carried out upon gradually varying the thickness of sputtered and MOCVD-regrown AlN, respectively. The crystalline-quality of both as-annealed and regrown AlN samples was investigated by varying thicknesses of as-sputtered AlN and regrown AlN: The optimal crystalline quality appears when the thickness of sputtered AlN is 400~600 nm. In addition, the stress states of all regrown samples are in agreement with these of post-annealed samples: which the tensile stress gradually evolves into compressive ones upon increasing thicknesses of as-sputtered AlN. The surfaces of all post-annealed samples were rebuilt as step-bunching morphology after MOCVD regrowth, and the surface roughness was found increased upon increasing thickness of regrown AlN layer. Our results act as the basement to understand the structural information of regrown AlN on high-temperature-annealed AlN templates.