Evidence of valence band perturbations in GaAsN/GaAs(001): A combined   variable-angle spectroscopic ellipsometry and modulated photoreflectance   investigation
  The contribution of the fundamental gap E_ as well as those of the E_ + Delta(so) and E+ transitions to the dielectric function of GaAs1-xNx alloys near the band edge were determined from variable-angle spectroscopic ellipsometry and modulated photoreflectance spectroscopy analyses. The oscillator strength of the E_ optical transition increases weakly with nitrogen incorporation. The two experimental techniques independently reveal that not only the oscillator strength of the E+ transition but also that of E_ + Delta(so) become larger compared to that of the fundamental gap as the N content increases. Since the same conduction band is involved in both the E_ transition and its split-off replica, these results reveal that adding nitrogen in GaAs1-xNx alloys affects not only the conduction but also the valence bands. 
S. Turcotte (1), S. Larouche (1), J.-N. Beaudry (1), L. Martinu (1),   R.A. Masut (1), P. Desjardins (1) and R. Leonelli (2)...