High-quality coalescence of laterally overgrown GaN stripes on GaN/sapphire seed layers

We have characterized GaN stripes grown by lateral epitaxial overgrowth on large-area (2 in.) SiO2/GaN/Al2O3 wafers by low-pressure metalorganic chemi cal vapor deposition before and after coalescence. Using scanning electron microscopy, x-ray diffraction (XRD), transmission electron microscopy (TEM) , and atomic force microscope (AFM), it is shown that by first obtaining "w ings" (laterally overgrown material) with low tilt relative to the "seed" ( underlying) GaN, very few extended defects are formed when wings from neigh boring stripes coalesce. After wings with a tilt of similar to 0.1 degrees are coalesced and an additional similar to 10 mu m of GaN is grown, it is f ound with XRD that peak splitting due to tilt is no longer detectable. TEM and AFM results show that few dislocations (with a linear density < 4x10(3) cm(-1)) are formed at coalescence fronts. (C) 1999 American Institute of P hysics. [S0003- 6951(99)01438-2].