Single nitrogen dyad magnetoluminescence in GaAs

Abstract

We report on the excitonic luminescence from two nearby nitrogen atoms (a dyad) in GaAs with and without an external magnetic field. The data are analyzed using a Hamiltonian taking into account the effects of the exchange interaction, the crystal field, and the Zeeman interaction and allowing the evaluation of the relative oscillator strength of the optical transitions and their polarization. Without the external magnetic field, we determine the exchange and crystal-field parameters characterizing the four excitonic states observed from dyads oriented along [110] or $[1\overline{1}0]$ and find that it is necessary to reduce the symmetry of all the terms involved in the Hamiltonian to the symmetry of the dyads $({C}_{2v})$. As expected from two smaller atoms, the parameters indicate a dyad under tensile strain. Although the degeneracy of all excitonic states is already lifted, the magnetic field allows a closer examination of the nature of these states. The small diamagnetic shift of $1.99\ifmmode\pm\else\textpm\fi{}0.06\text{ }\ensuremath{\mu}\text{eV}\text{ }{\text{T}}^{\ensuremath{-}2}$ is consistent with a strong localization of the electron to the nitrogen dyad and the $g$ factor of the electron is an intermediate value between that of a free electron in GaAs and a perfectly localized electron.