Structural and optical properties of epitaxially laterally overgrown a-plane GaN epilayer on SiO₂ stripe patterned r-plane sapphire

We have studied the structural anisotropic characteristics of epitaxially laterally overgrown (ELOG) a-plane GaN epilayer on r-plane sapphire substrate with two different SiO₂-stripe orientations using metal organic chemical vapor deposition. The SiO₂ stipe patterns were made along [0001] and [1100] crystographilic orientations of GaN which correspond to [1101] and [1120] directions of r-plane sapphire, respectively. The ELOG a-plane GaN on [0001]-stripe orientation reveals symmetric morphology in the extent of lateral overgrowth compared to that grown on [1100]-oriented stripe. Threading dislocation and basal stacking fault densities in wing region were ∼8 × 10⁷ cm^-2 and ∼5.2 × 10⁴ cm^-1, respectively. Raman measurement of the fully coalesced a-plane GaN indicated a compressive strain of about 0.39 Gpa in the window region.