Structural and optical properties of GaNAs/GaAs quantum well (QW) structures are studied by performing X-ray diffraction (XRD) and photoluminescence (PL) measurements. Arsenic-rich GaNAs layers were grown by molecular beam epitaxy with a water-cooled nitrogen plasma cell. The nitrogen content x of our GaNxAs1-x layers were in the range of 0.5-2%. Clear PL signals with a tail in the low energy side were observed fron 1 GaNxAs1-x/GaAs QWs. The positions of these PL peaks are roughly explained by theory using a reported bowing parameter. Electrical properties of a selectively doped GaAs/GaNxAs1-x/n-AlGaAs structure were also studied. It is found that electrons are accumulated in the GaNAs layer. The fluctuation of alloy compositions appears to have a dominant effect on electron mobilities.