The selective regrowth of GaN during sidewall-seeded epitaxial lateral overgrowth was performed. In addition to adjusting the V/III ratio, control of offset angle of the sidewall was found to be effective for realizing one-sidewall-seeded a-plane (11 (2) over bar0) GaN on r-plane (1 (1) over bar 02) sapphire. The number of coalescence regions on the grooves was reduced, and threading-dislocation and stacking-fault densities as low as 10(6)-10(7) cm(-2) and 10(3)-10(4) cm(-1), respectively, were successfully realized. (C) 2009 Elsevier B.V. All rights reserved.