Stress at the coalescence boundary of epitaxial lateral overgrown GaN

We have investigated stress fields in epitaxial lateral overgrown (ELO) GaN fabricated by metalorganic vapor phase epitaxy. An increased compressive stress was found at the coalescence boundary of two adjacent wings of ELO GaN using confocal micro-Raman spectroscopy. Voids present at the coalescence boundary were identified as major source for this stress concentration. Stress concentration in the vicinity of voids was illustrated using finite element analysis. Differences in stress and crystalline quality between wing and window areas of ELO GaN were also investigated.