Optical investigation of MBE grown Si-doped AlxGa1-xN as a function of nominal Al mole fraction up to 0.5

AlxGa1-xN epitaxial films were grown by gas source molecular beam epitaxy a nd investigated as a function of Al mole fraction. Cathodoluminescence, pho toluminescence, and optical absorption measurements were used to characteri ze 1 mum thick layers of AlxGa1-xN with nominal x values of 0.1, 0.1, 0.3, 0.4, and 0.5 as well as GaN and the AlN buffer layer. The GaN and AlxGa1-xN layers were doped with 1 x 10(18) cm(-3) of Si from a Knudsen source. Typi cal spectra contain a donor bound exciton peak with its phonon replicas and donor-acceptor pair (DAP) peaks. From the observed bound exciton peak posi tions and the absorption data, the band gap energies for the AlxGa1-xN were estimated. and these values were compared with the linearly extrapolated b and gaps. This study indicates that the MBE growth of 1 mum thick AlxGa1-xN layers provides good quality films for x values up to 0.3, and lesser qual ity films for x values above this mole fraction, requiring further improvem ent and,or modifications to the MBE growth technique to obtain quality AlxG a1-xN alloy material for semiconductor devices. Published by Elsevier Scien ce B.V.