LONG-RANGE ORDER IN ALXGA1-XN FILMS GROWN BY MOLECULAR-BEAM EPITAXY

The first observation of atomic long range ordering in AlxGa1-xN thin films grown by electron cyclotron resonance assisted molecular beam ep itaxy on sapphire and 6H-SiC substrates is reported. The phenomenon wa s investigated by studying the superlattice peaks (0001), (0003), and (0005) using x-ray diffraction. The relative intensity of these peaks was found to be largest for Al content in the 30%-50% range in qualita tive agreement with expectations for an ordered structure of ideal Al0 .5Ga0.5N stoichiometry. The average size of the ordered domains in the films was found to be within a factor of 4 of the films' thicknesses. The degree of ordering depends on the III/V flux ratio and exhibits a weaker dependence on Si doping. (C) 1997 American Institute of Physic s.