Selective area growth of GaN nanorods by using molecular beam epitaxy: Effect of growth temperature and Ga flux

Gallium-nitride (GaN) nanorods (NRs) were selectively grown on patterned Ti/Si(111) substrates by using plasma-assisted molecular beam epitaxy. The effects of the growth temperature and the Ga flux on the optical properties of the GaN NRs were investigated. Both the length and the diameter of the GaN NRs decreased with increasing growth temperature whereas the diameter of the GaN NRs remained constant and the length increased with increasing Ga flux. The photoluminescence spectra of GaN NRs grown under different experimental conditions exhibited emission peaks corresponding to neutral-donor-bound excitons (D^OX), donor-acceptor pair (DAP), and yellow luminescence (YL) bands at 3.477, 3.26, and 2.25 eV, respectively. Results demonstrate that the variation in the diameters of the GaN NRs has a greater influence on the defect concentration than the lengths of the NRs.