Growth of non-polar m-plane GaN pseudo-substrates by Molecular beam epitaxy

Abstract

Non-polar m-plane GaN films were grown by Plasma Assisted Molecular Beam Epitaxy on γ-LiAlO2 (100) substrates by a controlled coalescence of GaN nanocolumns obtained by a two-step process including a top-down nanopillars etching from a GaN buffer and a subsequent bottom-up overgrowth. Transmission electron microscopy data show a significant reduction of extended defects density in the coalesced film as compared to the initial GaN buffer, most likely due to a filter effect by the regrowth process on the nanopillars inclined walls. Low temperature photoluminescence spectra back this reduction by a strong intensity decrease of the stacking faults fingerprint emission peaks, while a very intense donor-bound excitonic emission at 3.472 eV, 2.8 meV wide, becomes dominant.