Selective-area growth of thin GaN nanowires by MOCVD

We report the selective-area growth (SAG) of Ga-polar thin GaN nanowires on patterned GaN/sapphire (0001) substrates using metalorganic chemical vapor deposition (MOCVD) with a continuous gas supply. It has been found that the anisotropy in the growth rates of the (0001) and the {1-100} facets of GaN reaches a maximum at low precursor flow rates for both Ga source and NH3. It has also been revealed that the SAG efficiency which is dependent on pattern fill-factor should be properly taken into account in order to grow thin GaN nanowires. Based on these findings, we demonstrate the growth of GaN nanowires with a diameter of 50 nm, which is the smallest reported so far by selective-area MOCVD. Optical properties of a single GaN nanowire have been investigated by low temperature micro-photoluminescence. It has been shown that an appropriate shell layer is effective to considerably improve the properties, suggesting the importance of controlling surface states. (C) 2012 Elsevier B.V. All rights reserved.