InGaN/GaN Multiple Quantum Wells on N-Polar μ-Platelets Grown on Graphene

We investigate the growth by metal–organic vapor phase epitaxy of InGaN/GaN multiple quantum wells on organized N-polar GaN μ-platelets on a graphene/SiO2/Si wafer. The structural properties of μ-platelets have been studied by transmission electron microscopy and reveal a Ga-polar inclusion located at the center. The μ-platelets exhibit convex top facets revealing special features of the growth mechanism on the N-polar surface. First, biatomic steps play a crucial role by increasing the growth rate, as the confinement of adatoms on small terraces enhances material incorporation. In the absence of biatomic steps, the growth rate is strongly limited. Second, we observe an In-content variation along terraces attributed to preferential adsorption above the downward biatomic step. According to the cathodoluminescence study, the central Ga-polar inclusion changes the morphology of quantum wells by creating pyramidal structures that favor high In-content incorporation and show long wavelength emission in the amber/red region.