Nitrogen species from radio frequency plasma sources used for molecular beam epitaxy growth of GaN

We have made a detailed study of the: optical spectroscopy of two different RF plasma sources used for the growth of GaN by molecular beam epitaxy. Our studies show that for both sources the predominant species present in the cavity are nitrogen atoms. The strongest optical emission occurs at 869 nm. We have also studied, in detail, the factors which influence the ion content of the flux. Two key parameters are the temperature of the wall of the cavity and the size of the holes in the aperture plate from which the species emerge into the vacuum. We have identified conditions under which the ion content can be made negligibly small and show that this results in films with improved optical properties.