Excitonic fine structure of out-of-plane nitrogen dyads in GaAs

We report on the excitonic photoluminescence from a nitrogen dyad of C2v symmetry located in a plane parallel to the emitted light wavevector (out-of-plane). We determine that the spectral signature of out-of-plane dyads is composed of five transitions linearly polarized along [1 0 0] or [0 1 0]. A sixth transition is in principle allowed but could not be observed due to its relatively low oscillator strength. However, a perturbation in the close vicinity of a dyad can significantly influence the fine structure and the polarization sequence of the emission and can bring out this sixth transition.