Deep-level structure of the spin-active recombination center in dilute nitrides

A Gallium interstitial defect (Ga\(_{\textrm{i}}\)) is thought to be responsible for the spectacular spin-dependent recombination (SDR) in GaAs\(_{1-x}\)N\(_x\) dilute nitride semiconductors. Current understanding associates this defect with two in-gap levels corresponding to the (+/0) and (++/+) charge-state transitions. Using a spin-sensitive photo-induced current transient spectroscopy, the in-gap electronic structure of a \(x\) = 0.021 alloy is revealed. The (+/0) state lies \(\approx\) 0.27 eV below the conduction band edge, and an anomalous, negative activation energy reveals the presence of not one but \textit{two} other states in the gap. The observations are consistent with a (++/+) state \(\approx\) 0.19 eV above the valence band edge, and a hitherto ignored, (+++/++) state \(\approx\) 25 meV above the valence band edge. These observations can inform efforts to better model the SDR and the Ga\(_{\textrm{i}}\) defect's local chemical environment.