Spectroscopic ellipsometry analysis of GaAs1 − xNx layers grown by molecular beam epitaxy

In this work, we present the effect of nitrogen incorporation on the dielectric function of GaAsN samples, grown by molecular beam epitaxy (MBE) followed by a rapid thermal annealing (for 90 s at 680 °C). The GaAs1 − xNx samples with N content up to 1.5% (x = 0.0%, 0.1%, 0.5%, 1.5%), are investigated using room temperature spectroscopic ellipsometry (SE). The optical transitions in the spectral region around 3 eV are analyzed by fitting analytical critical point line shapes to the second derivative of the dielectric function. It was found that the features associated with E1 and E1 + Δ1 transitions are blue-shifted and become less sharp with increasing nitrogen incorporation, in contrast to the case of E0 transition energy in GaAs1 − xNx. An increase of the split-off Δ1 energy with nitrogen content was also obtained, in agreement to results found with MOVPE GaAs1 − xNx grown samples.