Experimental studies of the conduction-band structure of GaInNAs alloys

In this paper, we carry out a comprehensive review of the nitrogen-induced modifications of the electronic structure of Ga_1−yIn_yN_xAs_1−x alloys. We study in detail the behaviour of the conduction-band effective mass as a function of Fermi energy, nitrogen content and pressure. From measurements of the plasma frequency for samples with different electron concentrations we have determined the dispersion relation for the lowest conduction band. We have also studied composition, temperature and pressure dependent optical absorption spectra on free-standing layers of Ga_1−yIn_yN_xAs_1−x (0 ≤ x ≤ 0.025 and 0 ≤ y ≤ 0.09) lattice-matched to GaAs. Spectroscopic ellipsometry measurements performed in a wide photon energy range from 1.5 to 5.5 eV have been used to determine the energy dependence of the dielectric function as well as the energies of E₁, E₀' and E₂ critical point transitions. Experiments have shown that nitrogen has a large effect on the dispersion relations and on the optical spectra for the conduction-band states close to the Γ point. A much smaller effect has been observed for X and L minima as well as for the valence-band states. We have compared our results with other available experimental data. The results are analysed in terms of the analytical band anti-crossing model as well as the local density approximation calculations and empirical pseudopotential models.