Elimination of wing tilt laterally overgrown GaN

Abstract

Wing tilt and associated defects at the coalescence boundary in GaN were completely eliminated in a maskless homoepitaxial overgrowth process, whereas SiO2-masked homoepitaxial overgrowth showed the same effects as samples grown on sapphire or SiC. X-ray diffraction and transmission electron microscopy were used to investigate the structures and defect behavior in the epitaxial layers. Crystallographic tilt and the generation of new dislocations with a-type Burgers vectors were observed in the SiO2-masked sample, consistent with the wing tilt phenomenon, while high crystal quality and dislocation-free layers were grown in the maskless process. This shows that the mask is the primary cause for tilt and dislocations during overgrowth, while lattice and thermal mismatch have a contributing but smaller role. The wing tilt phenomenon is completely eliminated via a homoepitaxial, mask-free scheme.