Preparation of large-area, high quality, free-standing GaN distributed Bragg reflectors

•A novel EC etching-annealing strategy is proposed for the preparation of high quality, free-standing GaN-based DBR membranes.•The mass-transport process is investigated during annealing in NH3 ambient.•The membranes fabricated by the etching-annealing method show intact stack structure and good optical performance. In this paper, we propose a strategy for the preparation of large-area, high quality, free-standing nanoporous (NP) GaN distributed Bragg reflector (DBR) membranes via electrochemical (EC) etching followed by annealing in NH3 ambient. In a centimeter-level macroscopic area, the free-standing DBR membranes show smooth and crack-free surface, which are attributed to curvature-driven mass-transport during the annealing. Due to high peak reflectivity (>80%) and low root-mean-square roughness (∼0.934 nm) of the DBR membrane, the separation strategy introduces a paradigm to prepare high quality, free-standing semiconductor membranes.