In this contribution the authors studied the optical properties of cubic AlxGa1-xN/GaN single and multiple quantum wells. The well widths ranged from 2.5 to 7.5 nm. Samples were grown by rf-plasma assisted molecular beam epitaxy on free standing 3C-SiC (001) substrates. During growth of Al0.15Ga0.85N/GaN quantum wells clear reflection high energy electron diffraction oscillations were observed indicating a two dimensional growth mode. They observe strong room temperature, ultraviolet photoluminescence at about 3.3 eV with a minimum linewidth of 90 meV. The peak energy of the emission versus well width is reproduced by a square-well Poisson-Schrödinger model calculation.