Free-standing GaN grown on epitaxial lateral overgrown GaN substrates

The use of high growth rate metalorganic vapor phase epitaxial GaN on epitaxial lateral overgrown GaN, laser lifted-off, for the fabrication of thick free-standing GaN substrates is explored. Analysis of the spatially resolved photoluminescence spectra as a function of sample thickness corroborates the improvement in material quality in the epitaxial lateral overgrown region. Luminescence quenching and the emergence of an additional donor bound exciton transition characterize the thick GaN layer grown at high growth rate. Stress in the sample, which was overall small due to the separation of the GaN from the substrate by laser lift-off, was found to be compressive near the GaN substrate top surface. Differences in stress between top and back surface of the GaN substrate were found to be as small as 0.1-0.2GPa.