Resonant Raman scattering in GaAsN: Mixing, localization, and impurity band formation of electronic states

Raman and TEM measurements on a thick GaAsN layer and on GaAsN/GaAs quantum well structures are reported. The scattering was excited close to resonance with the N-induced $E_{+}$ transition, and detected in both Stokes and anti-Stokes regions including the low-frequency range around the Rayleigh line. A broad continuous scattering due to acoustic phonons is observed on the thick GaAsN layer. Calculations of the Raman efficiency show that the localization and mixing of the resonant electronic states account well for the measured spectral line shapes. The localization length around a single nitrogen impurity is estimated and the impurity band formation discussed. Periodic oscillations of the scattered intensity are observed on the quantum well structures. They are analyzed in terms of Raman interference effects. The observed oscillations period, spectral envelope, and interference contrast are used to address the density distribution of the electronic states involved in the $E_{+}$ transition.