Micro-photoluminescence from V-shape inverted pyramid in HVPE grown GaN film

Abstract

We report the room-temperature micro-luminescence images from V-shaped inverted pyramids in undoped GaN films grown on (0001) sapphire substrate by hybrid vapor phase epitaxy. As the excitation laser spot at 325 nm was translated from the surface toward the center of the inverted pyramid along its slope, the center wavelength of the PL peak shows a trend of monotonic red-shift of from 373.9 nm to 379.1 nm. This could be attributed to the 3-dimensional release of stress and associated decrease of build-in piezoelectric field in the V-defects. A distinct and strong emission at 386.7 nm was observed at the apex of the V-defect. This could be originated from the threading dislocation at the onset of the defect.