Subliming GaN into Ordered Nanowire Arrays for Ultraviolet and Visible Nanophotonics

We report on the fabrication of ordered arrays of InGaN/GaN nanowire quantum disks by a top-down selective-area sublimation method. Using a combination of two-dimensional molecular beam epitaxy of InGaN/GaN quantum wells, electron beam lithography, and ultra-high vacuum sublimation techniques, we demonstrate that the position, geometry, and dimensions of nanowires can be finely controlled at nano-, micro-, and macroscales. Relying on structural data, we evaluate in particular the relative sublimation rates of GaN crystal planes that drive the nanowire formation, we assess the intrinsic limits of selective area sublimation for the fabrication of NW arrays, and we evaluate the homogeneity of the process across the wafer. Because the sublimation method preserves the crystal quality of the NW material, we show that InGaN/GaN NWs present good optical properties, which can be leveraged for photonic applications in the ultraviolet and the visible range. In particular, we demonstrate that it is possible to realize on the same wafer not only arrays of nanowires that individually support room-temperature lasing based on Fabry-Perot resonances, but also subwavelength nanowires that we integrate in photonic crystals for the realization of nanowire-induced nanocavities: