Chemical ordering in AlGaN alloys grown by molecular beam epitaxy

Aluminum gallium nitride alloys were grown by molecular beam epitaxy and their film composition, structure, and microstructure were investigated by Rutherford backscattering spectroscopy, atomic force microscopy, x-ray diffraction, and transmission electron microscopy. It was found that the ratio of group-III to group-V fluxes influences the relative incorporation of gallium and aluminum in the films. The transmission electron microscopy and x-ray diffraction studies revealed the existence of three types of spontaneously formed superlattice structures with periodicities of 2, 7, and 12 ML. While the 2 ML ordering is preferred under group-V rich conditions of growth, the 7 and 12 ML orderings were observed under group-III rich conditions of growth. (C) 2001 American Institute of Physics.