The behavior of a high density radical source for the plasma assisted molecular beam epitaxy of GaN and AlGaN compounds is studied and compared with the one of a conventional plasma source. Plasma light emission correlates with the GaN growth rate. Both attest to the better efficiency of the new source for producing active nitrogen species with resulting growth rates well beyond 1 mu m/h. The present study shows that GaN films with equivalent structural and optical quality can be grown even with a growth rate enhancement by a factor of 5. The purity of the grown films is investigated as well as point defects. Positron annihilation shows that plasma conditions can be tuned in order to limit the increase of the gallium-vacancy related complexes density by about 2x10(16) cm(-3) while reaching growth rates as high as 2.1 mu m/h. (C) 2015 Elsevier B.V. All rights reserved.