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 \(\left[ {1\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{1} 00} \right]\) crystographilic orientations of GaN which correspond to \(\left[ {\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{1} 101} \right]\) and \(\left[ {11\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{2} 0} \right]\) 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 \(\left[ {1\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{1} 00} \right]\)-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.