The bandgap energy of the dilute bismuth GaBi_xSb_1−x alloy depending on temperature

The bandgap energy of the dilute bismuth GaBi_xSb_1−x alloy vs. temperature is investigated in this study. Its reduced temperature-sensitiveness is because of the localized character of the valence band states (VBS). In order to describe the reduced temperature-sensitiveness of the bandgap energy, a new term including localized energy is added to Varshni's equation. It is found that the localized energy exhibits an increasing trend as the bismuth fraction increases, which indicates that the localized character of the VBS becomes strong with the increasing bismuth fraction. It is also found that the influence of the bismuth fraction on the temperature dependence of the bandgap energy of GaBi_xSb_1−x is smaller than that of GaBi_xAs_1−x. In addition, the element indium is undoubtedly a good candidate to lessen the bismuth fraction to realize that the spin-orbit-splitting (SOP) energy surpasses the bandgap energy in GaBi_xSb_1−x.