Composition Dependence of the Band Gap Energy of the Sb-Rich GaBi_xSb_1−x Alloy (0 ≤ x ≤ 0.26) Described by the Modified Band Anticrossing Model

Abstract

The impurity–host interaction and the impurity–impurity interaction exist in the Sb-rich GaBi_xSb_1−x alloy. It is found that the effect of impurity–impurity on the band gap energy can be neglected. The impurity–host interaction not only depends on the Bi content, but also on the content of the host material. In order to describe the band gap energy of the Sb-rich GaBi_xSb_1−x, the virtual crystal approximation for conduction band minimum (CBM) and the modified valence band anticrossing model for valence band maximum (VBM) are applied. It is also found that when the Bi content is about 0.259, the band gap energy of GaBi_xSb_1−x becomes 0 eV. In addition, it is found that the Г CBM depending on Bi content is much stronger than that of the Г VBM. It is relative to two factors. One is that the conduction band offset between GaSb and GaBi is much larger than the valence band offset. The other is that the energy difference between the Bi level and the Г VBM of GaSb is very large. The large energy difference usually leads to a weak coupling interaction between the Bi level and the Г VBM of GaSb, thus resulting in weak composition dependence of the Г VBM in the Sb-rich range.