Raman scattering study of GaN nanostructures obtained by bottom-up and top-downapproaches

Abstract

GaN nanocolumnar structures were grown by plasma-assisted molecular beam epitaxy(PAMBE) and also fabricated by electron cyclotron resonance reactive ion etching(ECR-RIE) of a compact GaN film parallel to the [111] direction of the Si(111) substrates.Scanning electron microscopy shows that the nanocolumns fabricated by PAMBE havea length of about 300–500 nm with diameters ranging from 20 to 150 nm whilenanowhiskers formed by RIE have diameters of 40–80 nm and a height between 1.4 and1.7 µm. A comparative study of the vibrational spectrum (including optical and interfacephonons) of the nanostructures using conventional macro-Raman and micro-Ramanscattering as well as surface-enhanced Raman scattering is presented.