Rapid relaxation of crystallographic anisotropy in SiO2-removed lateral epitaxial overgrown GaN layers

Abstract Conventional LEO GaN layers are generally known to exhibit strain anisotropy arising from the interaction between laterally overgrown GaN and SiO 2 masks. In an attempt to minimize the strain and its effects on crystallography, the oxide mask was etched out prior to coalescence between adjacent GaN wings. A second overgrowth step was subsequently performed to complete the fabrication of SiO 2 -removed LEO layers. No split peak in the ω -rocking curve of (0 0 0 2) plane, indicating a crystallographic tilt, was observed in the SiO 2 -removed LEO layers. A small difference in FWHM values of (0 0 0 2) peak still existed depending on the direction of SiO 2 stripe with respect to the rotation axis for X-ray measurement. This is attributed to a residual anisotropy strain produced at the initial stage of lateral growth. Moreover, the anisotropy strain drastically relaxed as a result of SiO 2 mask removal and the inevitable thermal treatment of floating GaN wings during the second overgrowth.