Optical properties evolution of GaN film grown via lateral epitaxial overgrowth

Abstract

Spatially resolved Raman scattering mapping and room-temperature cathodoluminescence (CL) mapping of GaN via epitaxial lateral overgrowth (ELOG) on a SiNx-masked GaN template grown on a sapphire substrate were studied. Scanning electron microscope (SEM) measurements show that the ELOG layer is coalesced. Plane view Raman mapping shows that the E2 (high) phonon intensity is stronger in the wing regions than in the window regions. Transmission electron microscopy (TEM) of a cross-section indicates the dislocation annihilation process. Furthermore, the intensity of Raman mapping on a cross-section of A1 (TO) phonon in the coalesced area is more increased than the GaN template. Interestingly, the cross-sectional CL image shows a butterfly shaped pattern that provides a comprehensive understanding of the variations in the point defect distribution during the ELOG GaN regrowth process.