In situ fabrication and blueshifted red emission of GaN:Eu nanoneedles

A vapour transport route for the in situ fabrication of Eu-doped GaN nanoneedles is reported. The nanoneedles are single crystals of hexagonal structure and they grow in the [100] direction. The typical taper of a nanoneedle (in diameter) varies from 5 nm to 1 μm with a length of up to a few microns. Energy-dispersive x-ray studies indicate that the Eu concentration doped into the GaN nanoneedles is ∼0.2 at.%. Photoluminescence spectra show that the nanoneedles have very strong red emission around 611 nm with a significant blueshift by 11 nm probably due to the nanostructures' small size and the surface states of the nanoneedles. The flow rate of ammonia is shown to have a large effect on the doping rate and photoluminescence of GaN:Eu nanoneedles