Effect of nitrogen in the electronic structure of GaAsN and GaInAs(N) compounds grown by molecular beam epitaxy

We have performed spectroscopic measurements in order to investigate the exciton localization mechanism and the bandgap energies of GaAsN in three regimes: (i) doped; (ii) intermediate doped-alloy; and (iii) alloy and the transition energies in strained GaInAsN/GaAs quantum wells laser structures. mperature photoluminescence spectrum of GaAsN layer in doped regime shows several features of excitons bound to nitrogen complexes. In the intermediate doped-alloy regime, these bound states are tightly coupled to form a wide band below the GaAsN bandgap energy. We have used the band anticrossing model to simulate the evolution of the GaAsN bandgap energies versus nitrogen composition. We have found that incorporation of 1% nitrogen shifts the bandgap energy of about 225 meV. The interband transitions in GaInAsN/GaAs quantum wells (QWs) structures are investigated using photovoltage measurements and can be identified using the envelope function formalism taking into account the effects of strain and the bandgap lowering due to the presence of nitrogen.