Deep-Level Structure of the Spin-Active Recombination Center in Dilute Nitrides

A gallium interstitial defect is thought to be responsible for the spectacular spin-dependent recombination in ${\mathrm{GaAs}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ dilute nitrides. Current understanding associates this defect with at least two in-gap levels corresponding to the ($+/0$) and ($++/+$) charge-state transitions. Using a spin-sensitive photoinduced current transient spectroscopy, the in-gap electronic structure of a $x=0.021$ alloy is revealed. The ($+/0$) state lies $\ensuremath{\approx}0.27\text{ }\text{ }\mathrm{eV}$ below the conduction band edge, and an anomalous, negative activation energy reveals the presence of not one but two other in-gap states. The observations are consistent with a ($++/+$) state $\ensuremath{\approx}0.19\text{ }\text{ }\mathrm{eV}$ above the valence band edge, and a ($+++/++$) state $\ensuremath{\approx}25\text{ }\text{ }\mathrm{meV}$ above the valence band edge.