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We have developed a method to fabricate GaN planar nanowires and cavities by combination of Focused Ion Beam (FIB) patterning of the substrate followed by Metal Organic Vapor Phase Epitaxy (MOVPE). The method includes depositing a silicon nitride mask on a sapphire substrate, etching of the trenches in the mask by FIB with a diameter of 40 nm with subsequent MOVPE growth of GaN within trenches. It was observed that the growth rate of GaN is substantially increased due to enhanced bulk diffusion of the growth precursor therefore the model for analysis of the growth rate was developed. The GaN strips fabricated by this method demonstrate effective luminescence properties. The structures demonstrate enhancement of spontaneous emission via formation of Fabry-Perot modes.

GaN planar nanowires (NWs) are fabricated by selective area metal-organic vapor phase epitaxy using focused ion beam etching of trench pattern in the Si 3 N 4 mask. Two crystallographic orientations of NWs along 11 20 ½ and 10 10 ½ directions are investigated. The coherent growth is confirmed for both directions; however, the best morphology, crystalline and optical properties are found in the GaN planar NWs fabricated along the 10 10 ½ axis. Cathodoluminescence (CL) at 5 K reveals a presence of Fabry-Perot modes in the region of 1.8-2.5 eV for the NWs fabricated in the 10 10 ½ direction. The position and intensity of the Fabry-Perot peaks vary depending on measured point within the NW, which is explained by the model based on the Purcell coefficient calculations. It is shown that small fluctuations in the NW thickness cause a noticeable shift of the Fabry-Perot modes energies, while the enhancement or reduction of the emission intensity for the Fabry-Perot peaks depend on the position of the emitter inside the planar NW.

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