Ultralong and Defect-Free GaN Nanowires Grown by theHVPE Process.

GaNnanowires with exceptional lengths are synthesized by vapor–liquid–solidcoupled with near-equilibrium hydride vapor phase epitaxy techniqueon c-plane sapphire substrates. Because of the highdecomposition frequency of GaCl precursors and a direct supply ofGa through the catalyst particle, the growth of GaN nanowires withconstant diameters takes place at an exceptional growth rate of 130μm/h. The chemical composition of the catalyst droplet is analyzedby energy dispersive X-ray spectroscopy. High-resolution transmissionelectron microscopy and selective area diffraction show that the GaNnanowires crystallize in the hexagonal wurzite structure and are defect-free.GaN nanowires exhibit bare top facets without any droplet. Microphotoluminescencedisplays a narrow and intense emission line (1 meV line width) associatedto the neutral-donor bound exciton revealing excellent optical propertiesof GaN nanowires. [ABSTRACT FROM AUTHOR]