The factors determining the band gap energy of the As-rich GaBixAs1-x

The band gap energy in the As-rich GaBi_xAs_1-x alloy is studied and a modified model is set up. It is found that the impurity-impurity interaction determined by the Bi pairs and Bi clusters should be taken into consideration. It is also found that when the Bi content increases, the band gap energy of GaBi_xAs_1-x goes through from the impurity-like region to the band-like region in the As-rich range. In the impurity-like region, the D VBM of GaBi_xAs_1-x plays a more important role than the D CBM in the band gap reduction. Under this condition, the impurity-host interaction in the valence band should be the most important factor to determine the band gap energy. On increasing Bi content, the D VBM of GaBi_xAs_1-x gradually shows a weaker composition dependence than D CBM due to the influence of the localized Bi levels. In this case, the most important factor determining the band gap energy is the impurity-host interaction in the conduction band.