Effect of SiO^sub 2^ hexagonal pattern on the crystal and optical properties of epitaxial lateral overgrown semipolar (11-22) GaN film

We studied the optical and crystal properties of semipolar (11-22) hexagonal epitaxial lateral overgrown (HELO) GaN films with different SiO2 hexagonal pattern widths (6-15 µm). With increasing SiO2 hexagonal pattern width, it was difficult to achieve coalescence and planarization of the semipolar HELO-GaN film. Furthermore, the surface root mean square roughness of the semipolar (11-22) HELO-GaN film increased with the increasing SiO2 hexagonal pattern width. With the increasing SiO2 hexagon pattern width, the full width at half maximum (FWHM) of the X-ray rocking curve (XRC) toward [1-100] decreased from 1474 to 721 arcsec, but the FWHM of XRCs toward [11-2-3] decreased to 9 µm, and then, increased with the SiO2 pattern width (> 12 µm). However, the PL intensity of the semipolar HELO-GaN film increased with the SiO2 hexagonal pattern width. From the findings of this study, we believe that the optical and crystal properties of the semipolar (11-22) HELO-GaN film would be significantly affected by the SiO2 hexagonal pattern width because of the friction between the GaN and SiO2 pattern during the coalescence and planarization step.