Preparation and properties of GaN:Al layers grown by radio-frequency magnetron sputter epitaxy.

Ga-rich Al x Ga 1– x N ( x « 0.01) (GaN:Al) single-crystalline layers were grown by radio-frequency magnetron sputter epitaxy using N 2 /Ar gas and a 6-N grade AlGa alloy target. When an Al 0.6 Ga 0.4 alloy was used as the target, the Al molar fraction in the AlGaN layer increased with the increase of substrate temperature; at temperatures >1000 °C, it increased to more than 60% of the Al molar fraction of AlGa target. For an Al 0.1 Ga 0.9 alloy target, the Al molar fraction in the AlGaN layer was less than 10% of the Al molar fraction of the target material. The GaN:Al layers, similar to GaN layers, could be grown at 900 °C and 3–12% N 2 composition ratios in N 2 /Ar ambient gas using an Al 0.1 Ga 0.9 target. The full-width at half-maximum (FWHM) value of the X-ray rocking curve (XRC) of the GaN:Al layer grown at 6% N 2 , was 28 and 368 arcsec for highly c -axis-oriented columnar domains and disordered structures inside the GaN:Al layer, respectively, for the (0002) plane. The FWHM (XRC) of the GaN:Al layer grown at 10% N 2 was 600 and 1320 arcsec for the disordered structure and/or the partially relaxed portion. The threading dislocation densities depended on the N 2 composition ratio. [ABSTRACT FROM AUTHOR]