Surface superstructures and optical properties of wurtzite GaN grown on 6H-SiC

Abstract

We report on the surface reconstructions on the basal planes of wurtzite GaN. Depending on the surface polarity, two distinct classes of reconstructions form. The Ga-polar surface displays the Ga fluid-1×1, 10×10, 5√3×2√13, 5×5, 4×4, and 2×2, and the (0 0 0 1 ̄ ) N-polar surface the 6×8, 6×6, √7×√7 and 2×3 with decreasing surface Ga coverage. We will show that their structure is consistent with a simple Ga-adatom-based scheme. Crystalline structure and optical properties of the GaN epilayers are examined by high resolution X-ray diffraction and photoluminescence, and the results reveal a strong relation between the threading-dislocation density and the intensities of both near-band transition at 3.427 eV and yellow luminescence at 2.16 eV.