Band gap energy of the As-rich InxGa1-xBiyAs1-y depending on composition

Abstract

A model estimating the band gap energy of the As-rich InxGa1-xBiyAs1-y is set up. An excellent description is shown. It is found that the In and Bi fractions do not modify the Г valence band maximum (VBM) independently. However, they modify the Г conduction band minimum (CBM) independently. The incorporation of the In fraction in the GaBiyAs1-y alloy will lead to the coupling interaction between the Bi level and the Г CBM of the host material decreasing. It is due to that the energy difference between the Bi level and the Г VBM of InxGa1-xAs enlarges with increasing In fraction. InxGa1-xBiyAs1-y needs less Bi fraction than GaBiyAs1-y when the spin–orbit splitting energy surpasses the band gap energy. The reason is that incorporating In fraction in GaBiyAs1-y can reduce the band gap energy while the spin–orbit splitting energy almost keeps a constant. In addition, the impurity-host interaction depends on not only the impurity anion fraction, but also the host anion fraction when the impurity anion fraction reaches a certain degree. If there are two or more cations in the alloy, the coupling parameter depending on the cation fraction should be taken into consideration. Based on the existing evidence, it can be concluded that InxGa1-xBiyAs1-y has a direct band gap in the whole composition range.