Growth and characterization of GaN nano-columns grown on gallium-coated Si (111) by using molecular beam epitaxy

Vertically-aligned gallium-nitride nano-columns were grown on a gallium-coated silicon substrate by using molecular beam epitaxy. The dense packing of the nano-columns gives them the appearance of a continuous film in a surface view, but a cross-sectional analysis shows them to be isolated nanostructures possessing a pyramid like tip. The diameter and the length of the GaN nano-columns were about 100 nm and 0.7 - 1 μm, respectively. From the photoluminescence measurement of nano-columns, a narrow peak at 363 nm with a full width at half maximum of 63 meV related to excitonic emission was observed. From the Raman spectrum, the phonon peak at 566.9 was assigned to the E ₂ phonon mode of GaN, which clearly indicates that the GaN nano-columns are well grown. From the above result, it is evident that the grown nano-columns are highly crystalline and are aligned perpendicular to the silicon surface.