Effects of Different Plasma Species (Atomic N, Metastable N*2, and Ions) on the Optical Properties of Dilute Nitride Materials Grown by Plasma-Assisted Molecular-Beam Epitaxy

This letter studies the effects of atomic N, metastable N2*, and ionic species on the optical properties of dilute nitride materials. Ga0.8 In0.2 N0.01 As0.99 was grown using a 1% N2 in Ar gas mix from an Applied-Epi Unibulb rf plasma source. Isonitrogen samples with and without ions were studied using various plasma operating conditions. Optical emission spectrometry was used to characterize relative proportions of different active nitrogen plasma species (atomic N and metastable N2*). Samples grown without ions and with a higher proportion of atomic N resulted in the best overall material quality, although this improvement was observed at high annealing temperatures. At lower annealing temperatures, increased blueshifts were observed for samples grown with a higher proportion of atomic N; however, there was no noticeable influence of ions on blueshift regardless of whether atomic N or metastable N2* was the dominant species present in the plasma. The key implication of this work is that it helps to elucidate a possible reason for some of the contradictory reports in the literature. The ions are not solely responsible for the commonly reported "plasma damage." Furthermore, we demonstrate herein that atomic N and metastable N2* each have different effects on the optical properties of dilute nitride materials grown by plasma-assisted molecular-beam epitaxy.