RF-MBE growth of Si doped cubic GaN and hexagonal phase incorporated c-AlGaN films on MgO(0 0 1) 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 2.8×10²⁰ cm^-3 for c-GaN and 1.3×10²⁰ cm^-3 for c-AlGaN (Al content of 710% 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 cm²/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.