Onset of tetrahedral interstitial formation in GaAsN alloys

Due to the dramatic bandgap reductions induced by dilute N concentrations, dilute nitride alloys are useful for near-to-mid-infrared devices. However, several studies have linked non-substitutional N incorporation to diminished absorption and emission efficiencies. Meanwhile, most computational studies have focused on the relative stabilities of substitutional nitrogen (NAs) and (N-N)As and (N-As)As split interstitials, with minimal consideration of N tetrahedral interstitials (Ntetra). To date, (N-As)As and (N-N)As have been observed via channeling NRA (NRA/c) and x-ray photoelectron spectroscopy (XPS). However, direct detection of Ntetra has not been reported. Here, we probe N incorporation mechanisms using combined experimental and computational NRA and Rutherford Backscattering spectrometry (RBS) angular yield scans. For xN< 0.025, both NAs and split interstitials are observed. However, for xN ≥ 0.025, evidence for Ntetra emerges. We discuss the possible role of interacting strain fields between N atoms as the driving force for Ntetra incorporation. This work opens opportunities for consideration of Ntetra and its influence on the properties of a variety of highly mismatched alloys.