Material and optical properties of trenched epitaxial lateral overgrowth of a-plane GaN

The crystal quality of a-plane GaN film was successfully improved by using trenched epitaxial lateral overgrowth (TELOG) of a-plane GaN. Not only the threading dislocation density but also the difference of anisotropic in-plane strain between orthogonal crystal axes can be mitigated by using TELOG. The low threading dislocation density investigated by transmission electron microscopy was estimated to be 3 × 10⁷ cm^-2 on the N-face GaN wing. According the results of μ-PL and CL, the threading dislocations are the strongly non-radiative center in a-plane GaN film. Finally, we concluded that a narrower stripped GaN seeds and deeper stripped trenches etched into the surface of sapphire could derive a better quality a-plane GaN film.