Luminescence of structured InN deposited on graphene interlayer

Abstract

Indium nitride epilayers were grown by metalorganic chemical vapour deposition (MOCVD) on graphene/SiC substrates with different terrace widths. Photoluminescence (PL) properties in the epilayers of different thickness and along the epilayer growth direction were studied with spatial resolution using confocal microscopy. The PL properties have been linked with the structure of the epilayers studied by X-ray diffraction, transmission electron microscopy, atomic force microscopy and Raman scattering. It is revealed that InN on graphene/SiC layers with a thickness of up to ~2 μm consists of chaotically oriented nanocrystals of 20 nm in diameter but tends to transform into a more homogeneous multicrystalline layer at longer deposition durations. The PL band in the top part of thick layers is peaked at 0.687 eV, closer to the band gap than in any InN epilayer grown by MOCVD before. This evidences a low density of equilibrium electrons usually deteriorating performance of InN epilayers. The PL band in thin samples or in the lower part of thick samples is shifted by 60 meV predominantly to quantum confinement in the nanocrystals.