Defect-controlled growth of GaN nanorods on (0001) sapphire by molecular beam epitaxy

Transmission electron microscopy is used to reveal threading defects in single crystal c-oriented GaN nanorods grown on (0001) sapphire by molecular beam epitaxy. The defects are shown to be planar faults lying on {10 (1) over bar0} planes and bounded by opposite partial screw dislocations with Burgers vectors of 1/2 < 0001 >. The faults nucleate, as dislocation half-loops, from points close to the GaN/(0001) sapphire interface. It is proposed that the spiral growth of the partial atomic step joining the emerging dislocations controls nanorod growth and accounts for the growth surface morphology. The significance of these defects for nanorod growth and applications is discussed. (C) 2008 American Institute of Physics.