RF-MBE growth of Si doped cubic GaN and hexagonal phase incorporated c-AlGaN films on MgO(001) substrates

Silicon doped cubic GaN (c-GaN) films were grown on MgO (0 0 1) substrates by radio-frequency-plasma-assisted molecular beam epitaxy (RF-MBE). And the incorporation of hexagonal phase into cubic AlGaN (c-AlGaN) films was examined. The conduction type of the Si doped c-GaN and c-AlGaN films was n-type. The maximum electron concentration was 2.8 x 10(20) cm(-3) for c-GaN and 1.3 x 10(20) cm(-3) for c-AlGaN (Al content of 7-10% and hexagonal phase of about 30%). The cubic phase purity of the films was maintained near the value of undoped films of the same Al content. The maximum electron mobility was 27 cm(2)/V s for c-GaN and electron mobility decreased as the cubic phase purity of the film decreases. The main cause of electron scattering is the stacking faults associated with the hexagonal phase incorporation. (C) 2011 Elsevier B.V. All rights reserved.