We have investigated the influence of an additional bismuth flux during growth on the properties of GaN films prepared by plasma-assisted molecular beam epitaxy (MBE). A wide range of bismuth fluxes have been used, the highest Bi flux was larger than the flux of Ga. We have demonstrated that using a Bi flux during the growth of GaN by MBE at a temperature similar to 800degreesC improves the surface morphology of the films and decreases the deep emission, We have demonstrated for the first time the growth of GaN1-xBix alloys by MBE, the Bi concentration was small and increased with decreasing growth temperature. We have studied the influence of an additional bismuth flux on the growth of As-doped GaN layers and observed an increase of blue emission from the layers at some optimum range of Bi fluxes. All the results allow us to conclude that Bi may be a potential new dopant for the growth of GaN by MBE. (C) 2002 Elsevier Science B.V. All rights reserved.