High-quality InGaN/GaN multiple-quantum wells (MQWs) with different In fractions varying from 0.04 to 0.30 have been grown on Ga-polarity GaN by N2 plasma-assisted molecular-beam epitaxy (rf-MBE). High-resolution x-ray diffraction results have indicated that the high interface quality and good reproducibility of the InGaN QW have been achieved. Photoluminescence spectra reveals the superior and intense luminescence properties of InGaN MQWs from ultraviolet (∼388 nm) to green-yellow (∼528 nm) range. We have shown that the Ga-polarity GaN underneath is the key parameter for the successful growth of InGaN MQWs by rf-MBE. © 2001 American Institute of Physics.