UC Santa Barbara

This letter reports on the reduction in extended-defect densities in a-plane (11 (2) over bar0) GaN films achieved via lateral epitaxial overgrowth (LEO) by hydride vapor phase-epitaxy. A variety of dielectric mask patterns was used to produce 8-125-mum-thick, fully coalesced nonpolar GaN films. The nanometer-scale pit densities in the overgrown regions were less than 3x10(6) cm(-2) compared to similar to10(10) cm(-2) in the direct-growth a-plane GaN. Cathodoluminescence revealed a fourfold increase in luminous intensity in the overgrown material compared to the window material. X-ray rocking curves indicate the films were free of wing tilt within the sensitivity of the measurements. Whereas non-LEO a-plane GaN exhibits basal plane stacking fault and threading dislocation densities of 10(5) cm(-1) and 10(9) cm(-2), respectively, the overgrown LEO material was essentially free of extended defects. The basal plane stacking fault and threading dislocation densities in the wing regions were below the detection limits of similar to5x10(6) cm(-2) and 3x10(3) cm(-1), respectively. (C) 2003 American Institute of Physics.