Growth of High Mobility AlGaN/GaN Heterostructures by Ammonia-Molecular Beam Epitaxy

Abstract

The growth of high mobility AlGaN/GaN heterostructures on insulating C-doped GaN base layers by ammonia-molecular beam epitaxy (ammonia-MBE) is reported. The structures were grown using an initial ∼300 Å buffer layer of AlN grown by Magnetron Sputter Epitaxy. This was followed by the deposition of GaN and AlGaN epilayers using ammonia-MBE. Semi-insulating C-doped GaN layers with resistivities greater than 106 Ω cm have been obtained using a methane ion source. Room temperature mobilities of up to 1211 cm2/Vs and 77 K mobiltitties of up to 5660 cm2/Vs have been measured for the two-dimensional electron gas in the heterostructures grown. Well-resolved Shubnikov-de Haas oscillations have been observed in the low temperature magnetoresistance measurements.