Improving the Optical Properties of Self-Catalyzed GaN Microrods toward Whispering Gallery Mode Lasing

GaN microrods were grown self-catalyzed by a fast and metal-organic vapor phase epitaxy method without microrods with a regular hexagonal cross-section, sharp edges, straight, and smooth sidewall facets act as a microresonator, as seen by the appearance of whispering gallery modes in the yellow defect band range. To improve their optical properties, a reduced Ga precursor flow is required during growth. However, their hexagonal microrod morphology is not maintained under these growth conditions. The approach to start growth a high Ga precursor flow and applying a ramp to a reduced precursor flow yield in significant enhancement of the near band edge emission in the upper part of the microrods. Whispering gallery modes in superposition with stimulated emission of a single whispering gallery mode up to similar to 2 MW/cm(2) and multimodel lasing with a threshold of 2.86 MW/cm(2) from an as-grown microrod under optical excitation at room temperature