Influence of radio frequency plasma cell conditions on the incorporation of nitrogen into GaAsN and GaInAsN

We have studied the influence of rf plasma cell operating conditions on the plasma assisted molecular beam epitaxy growth of bulk GaAsN and GaInAsN quantum wells. A plasma physics approach together with optical spectroscopy of the plasma emission lines and bands have been performed in order to understand the mechanisms of nitrogen incorporation and material deterioration. Both atoms and molecules do participate in the incorporation of N into the growing material. For high N2 flow rates, the species that mostly incorporate are vibrationaly excited molecules of the N2(X,v) ground state. The characteristic vibrational temperature of the N2(X,v) ground state has been found to be higher than 104K. For low N2 flow rates, the species that mostly incorporate are atoms and the dissociation fraction of N2 for the lowest flow rate and the highest rf power has been found to be up to 0.7. Finally, the ion damage has been decreased by increasing the N2 pressure, which induces a decrease of the electron temperature and consequently a decrease of the plasma ionization.