The photoluminescence from GaAsN/GaAs, where the N content was less than 0.5%, was studied. The low-temperature photoluminescence spectra comprised several excitons which were bound to N complexes; each of which was associated with a different composition or configuration. These features were studied as a function of the excitation intensity, temperature, concentration and growth conditions. The dependence of the binding energy, of the predominant recombination center, upon the N concentration was explained in terms of a hierarchy of N complexes; from centers which comprised at least two N atoms, to more extended clusters. These excitonic transitions were very sensitive to the growth parameters and could be used to study the statistical distribution of N in nominally uniform layers. It was also shown that a transition from N doping, to alloy formation, occurred for N concentrations above 0.25%.

Excitons Bound to Nitrogen Clusters in GaAsN. S.Francoeur, S.A.Nikishin, C.Jin, Y.Qiu, H.Temkin: Applied Physics Letters, 1999, 75[11], 1538-40