High-quality AlGaN/GaN grown on sapphire by gas-source molecular beam epitaxy using a thin low-temperature AlN layer

Growth of high-quality AlGaN/GaN heterostructures on sapphire by ammonia ga s-source molecular beam epitaxy is reported. Incorporation of a thin AIN la yer grown at low temperature within the GaN buffer is shown to result in en hanced electrical and structural characteristics for subsequently grown het erostructures. AlGaN/GaN structures exhibiting reduced background doping an d enhanced Hall mobilities (2100, 10310 and 12200 cm(2)/Vs with carrier she et densities of 6.1 x 10(12) cm(-2), 6.0 x 10(12) cm(-2), and 5.8 x 10(12) cm(-2) at 300 K, 77 K, and 0.3 K,respectively) correlate with dislocation f iltering in the thin AM layer. Magnetotransport measurements at 0.3 K revea l well-resolved Shubnikov-de Haas oscillations starting at 3 T.