Cubic AlxGa1-xN was grown on a GaAs (100) substrate by using low-pressure metalorganic vapor-phase epitaxy with a GaN buffer layer grown at low and high temperatures. The high-growth–temperature GaN layer improved the quality of the cubic AlxGa1-xN. Also, the AlN molar fraction could be controlled by changing the carrier gas flow of trimethylaluminum. The AlxGa1-xN epitaxial layers in the range of 0≤x≤0.23 exhibited strong near-band-edge photoluminescence at room temperature. Their photoluminescence peak energies show a linear dependence on the molar fraction. © 1997 American Institute of Physics.