First-Principle Tight Binding-Like Parametrizations of GaAs$_{\mathrm{1-x}}$Bi$_{\mathrm{x}}$ and InAs$_{\mathrm{1-x}}$Bi$_{\mathrm{x}}$ Electronic Structures

The anion substitution with Bi atoms in large concentration (1-5{\%}) has been proven to be an effective means for tuning the energy bandgap and the spin-orbit in materials like GaAs and InAs. In order to describe these materials in opto-electronic device simulations it is necessary to use simple and accurate parametrizations of their bandstructures. We describe here tight binding--like parametrizations of first-principle bandstructures to compare the better-know GaAs$_{\mathrm{1-x}}$Bi$_{\mathrm{x}}$ with the newer InAs$_{\mathrm{1-x}}$Bi$_{\mathrm{x}}$. Accurate bandgaps are included via hybrid density functionals, and spin-orbit split-offs of the valence bands as well as the d-orbitals for In are found to be crucial. Essential features such as the strong perturbation of the Luttinger Hamiltonian and the strong anticrossing between valence bands and impurity d-orbitals are captured in a zone-unfolding picture.