Controlled growth mode of high-aspect-ratio GaN nanorods by Ni/In/Ga catalyst

Abstract

Gallium nitride nanorods (GaN NRs) were grown by employing a low melting point Ni/In/Ga alloy via metalorganic chemical vapour deposition. A small growth temperature window was observed in the range of 720–765 °C, which is lower than typical temperatures used for the growth of GaN NRs assisted by metal catalyst. Tapered GaN NRs with triangular cross-section were produced at 750 °C by vapour–solid (VS) growth mechanism. A slight increase of temperature to 765 °C was able to change the growth mode to vapour–liquid–solid (VLS) and quasi-aligned GaN NRs with high aspect ratio were produced. Photoluminescence of both GaN NR morphologies measured at 10 K revealed only near band edge emission centred at 3.48 eV, which was blue-shifted from that of the bulk GaN estimated at 3.46 eV. Micro-Raman spectroscopy performed at 300 K exhibited that GaN NRs grown either by VS or VLS growth mechanisms are relatively free of strain.