HIGH-QUALITY SELF-NUCLEATED ALXGA1-X N LAYERS ON (00.1) SAPPHIRE BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION

High quality Al(x)Ga1-xN alloy films with x<0.4 have been prepared on self-nucleated (00.1) sapphire substrates by low-pressure metalorganic chemical vapor deposition. It has been shown that the lattice constant of the films varies linearly with alloy composition x (Vegard's law is obeyed) and that homogeneous and inhomogeneous strain and alloy clustering are minimized in these self-nucleated Al(x)Ga1-xN films. Consistent with their reduced strain and chemical uniformity, the derived optical band gaps of these Al(x)Ga1-xN films also show a linear dependence on alloy composition x, yielding a bowing parameter b almost-equal-to0 eV. (C) 1994 American Institute of Physics.