Theory of the electronic structure of dilute bismide and bismide-nitride alloys of GaAs: Tight-binding and k.p models

The addition of dilute concentrations of bismuth (Bi) into GaAs to form GaBixAs1−x alloys results in a large reduction of the band gap energy (Eg) accompanied by a significant increase of the spin-orbit-splitting energy (ΔSO), leading to an Eg < ΔSO regime for x ∼ 10% which is technologically relevant for the design of highly efficient photonic devices. The quaternary alloy GaBixNyAs1−x−y offers further flexibility for band gap tuning, because both nitrogen and bismuth can independently induce band gap reduction. This work reports sp3s* tight binding and 14-band k⋅p models for the study of the electronic structure of GaBixAs1−x and GaBixNyAs1−x−y alloys. Our results are in good agreement with the available experimental data.