Modifying optical properties of GaN nanowires by Ga2O3 overgrowth

The authors report on the modification of optical properties of GaN nanowires by growing a thin Ga2O3 overlayer on GaN surface, forming a core/shell heterostructure. The GaN/Ga2O3 core/shell nanowires were formed first by the axial growth of GaN nanowires, followed by the radical growth of the Ga2O3 overlayer. The GaN core possesses single crystalline wurtzite structure, whereas the Ga2O3 shell layer is monoclinic polycrystalline. For the GaN/Ga2O3 core/shell nanowires, a pronounced blueshift of the Raman A(1)(LO) mode was found, indicating a compressive stress on the core wire due to the lattice mismatch with the outer shell. This picture is also supported by the photoluminescence spectrum, in which the peak shifts to higher energy after the overgrowth of Ga2O3 on GaN. (C) 2012 American Vacuum Society. [DOI: 10.1116/1.3668122]