Stress distribution in GaN nanopillars using confocal Raman mapping technique

Abstract

In this Letter, high-resolution confocal Raman mapping of stress distribution in etched and re-grown GaN nanopillar structures is investigated. Results of the E2(high) phonon line mapping of the top surfaces of individual nanopillars reveal differences in stress between both the center and edge of the nanopillar top surfaces and between the etched and re-grown GaN nanopillar structures. In-plane biaxial compressive stress with the values of 0.36–0.42 GPa and 0.49–0.54 GPa is observed at the center of etched and re-grown GaN nanopillars, respectively. The in-plane biaxial compressive stress decreases from center to edge in re-grown GaN nanopillar due to the tilted facets. Also, the A1(LO) phonon frequency increases from center to edges, or tilted facets, due to the tilt of the c-axis of re-grown GaN nanopillar.