Epitaxial Al/GaN and Au/GaN junctions on as-grown GaN(0001)1 × 1 surfaces

GaN(0001) epilayers were fabricated by rf-plasma enhanced molecular beam epitaxy on GaN templates. The templates were grown by metalorganic chemical vapor deposition on sapphire. The layers exhibited the 2 × 2 reconstruction of the Ga-face during growth and the 1 × 1 reconstruction upon cooling. On such surfaces, Al/n-GaN and Au/n-GaN junctions were fabricated in-situ by molecular beam epitaxy. X-ray photoemission spectroscopy studies allowed us to determine n-type Schottky barrier heights of 0.61 ± 0.06 and 0.98 ± 0.06 eV, respectively, for the two types of epitaxial junctions.