Hydride Vapor Phase Epitaxy (HVPE) growth process is still efficient for the growth of high quality GaN material. In situ characterization techniques are extremely difficult to implement inside HVPE hot wall reactors. A method based on selective area growth coupled to spatially resolved optical spectroscopies, micro-photoluminescence and micro reflectivity is developed for a control of GaN optical quality and strain at different growth stages. As highly reproducible HVPE process is used with a two-step epitaxial lateral overgrowth procedure to produce 80 pm thick GaN layers presenting a weak residual strain with high optical quality comparable to free-standing GaN layers. (C) 2015 Elsevier B.V. All rights reserved,