Characterisation of epitaxial laterally overgrown gallium nitride using transmission electron microscopy

We describe structural characterisation of epitaxial laterally overgrown (E LOG) GaN by transmission electron microscopy. A reduced dislocation density is observed in laterally overgrown GaN, although dislocations are observed at the centre of the overgrown region, associated with the coalescence of GaN growth fronts. Dislocations which propagate into the overgrown GaN bend over into the basal plane. Where surface pits are present, they are usuall y hexagonal in shape, bounded by {10 (1) over bar 1} planes, and lie above the silica stripes along the line of coalescence. Threading dislocations ar e commonly found to emerge at the base of these pits. The light output of L EDs made from ELOG GaN is 40 times greater than that from comparable conven tionally grown, high dislocation density GaN.