Effects of strain on the band structure of group-III nitrides

We present a systematic study of strain effects on the electronic band structure of the group-IIInitrides (AlN, GaN and InN). The calculations are based on density functional theory (DFT) with band-gap-corrected approaches including hybrid functional and quasiparticle G0W0 methods. We study strain effects under realistic strain conditions, hydrostatic pressure and biaxial stress. The strain-induced modification of the band structures is found to be nonlinear; transition energies and crystal-field splittings show a strong nonlinear behavior under biaxial stress. For the linear regime around the experimental lattice parameters, we present a complete set of deformation potentials (acz, act, D1, D2, D3, D4, D5, D6) that allows us to predict the band positions of group-III nitrides and their alloys (InGaN and AlGaN) under realistic strain conditions. We quantify the nonlinearity of strain effects by introducing a set of bowing parameters. We apply the calculated deformation potentials to the prediction of strain effects on transition energies and valence-band structures of InGaN alloys and quantum wells grown on GaN, in various orientations (including c-plane, m-plane, and semipolar). The calculated band gap bowing parameters including the strain effect for c-plane InGaN agrees well with the results obtained by hybrid functional alloy calculations. For semipolar InGaN QWs grown in (2021), (3031), and (3031) orientations, our calculated deformation potentials have provided results for polarization ratios in good agreement with the experimental observations, providing further confidence in the accuracy of our values.