The crystal quality of a-plane GaN films was improved by using epitaxial lateral overgrowth on trenched a-plane GaN buffer layers. Not only the threading dislocation density, but also the difference in anisotropic in-plane strain between orthogonal crystal axes could be mitigated by using trenched epitaxial lateral overgrowth. The low threading dislocation density, investigated by means of cross-sectional transmission electron microscopy, was estimated to be 3 x 107/cm2 on the N-face GaN wing. On the other hand, the Ga-face GaN wing, with its faster lateral overgrowth rate, could be influenced by the thin GaN layer grown on the bottom of the trenches. This resulted in higher dislocation density generation. As a result, it was concluded that narrower stripped GaN seeds and deeper stripped trenches etched into the surface of sapphire could give better-quality a-plane GaN films. The fast coalescence of trenched epitaxial lateral overgrown GaN films below 10µm in thickness was demonstrated.

Trenched Epitaxial Lateral Overgrowth of Fast Coalesced a-Plane GaN with Low Dislocation Density. T.C.Wang, T.C.Lu, T.S.Ko, H.C.Kuo, M.Yu, S.C.Wang, C.C.Chuo, Z.H.Lee, H.G.Chen: Applied Physics Letters, 2006, 89[25], 251109 (3pp)