Influence of substrate nitridation on properties of GaN nanorods grown on molybdenum foil by laser molecular beam epitaxy

Abstract

We studied the effect of nitridation condition of Mo foil on the properties of GaN nanorods grown by laser molecular beam epitaxy. It is found that randomly size-distributed three-dimensional GaN islands were grown on bare Mo foil at growth temperature of 700 °C. Upon nitridation of Mo foil with low nitrogen plasma flux, hexagonally-faceted inverse-tapered GaN nanorods were grown whereas tapered GaN nanorods were obtained for Mo foil nitridated under high nitrogen plasma flux. Using wet-chemical etching process, it is deduced that the inverse-tapered GaN nanorods have N-polarity while the tapered GaN nanorods have Ga-polarity. Optical analysis revealed that the inverse-tapered GaN nanorods have prominent near band edge (NBE) emission peak with negligible defect-related peaks whereas tapered GaN nanorods possess yellow luminescence peak along with NBE emission. The control of polarity of GaN nanords on flexible metal foils by tuning pre-nitridation condition is beneficial for futuristic nitride-based flexible opto-electronics devices.