Emission Properties of GaN Planar Hexagonal Microcavities

Fabrication of microcavities based on III‐nitrides is challenging due to difficulties with the coherent growth of heterostructures having a large number of periods, at the same time keeping a good precision in terms of thickness and composition of the alloy. A planar design for GaN microresonators supporting whispering gallery modes is suggested. GaN hexagonal microstructures are fabricated by selective‐area metalorganic vapor phase epitaxy using focused ion beam for mask patterning. Low‐temperature cathodoluminescence spectra measured with a high spatial resolution demonstrate two dominant emission lines in the near bandgap region. These lines merge at room temperature into a broad emission band peaking at ≈3.3 eV, which is shifted toward lower energies compared with the reference excitonic spectrum measured for the GaN layer. A numerical analysis of exciton–polariton modes shows that some strongly localized cavity modes can have high Purcell coefficients and can strongly interact with the GaN exciton. GaN planar hexagonal microcavities are fabricated using metalorganic vapor phase epitaxy. Almost ideal hexagons exhibit the properties of microresonators that support whispering gallery modes. Near bandgap cathodoluminescence spectra indicate a modification of the exciton emission compared with the GaN layer emission due to interaction with cavity modes.