BAND ALIGNMENT FOR AMBIPOLAR-DOPING OF PbxZn1-xTe ALLOYS: A FIRST-PRINCIPLE STUDY

Using a first-principle band-structure method and a special quasirandom structure (SQS) approach, we present state-of-the-art HSE06 functional calculations for demonstrating the possibility of ternary PbxZn1-xTe alloys to be bipolar-doping materials. The results show that the bowing parameters and the band gaps of these alloys sensitively depend on the composition x. Due to the full overlapping and delocalization, the coupling between Pb outermost p orbits and Zn 4s orbits become very strong, thus resulting in a significant downshift of conduction band edge with the increase of Pb concentration x. When the concentration x reaches 0.25, it is demonstrated that the Pb0.25Zn0.75Te alloy has a substantial decrease in the conduction band edge, while leaving the valence band edge almost unchanged compared to that of binary ZnTe, thus improving the possibility for ambipolar-doping. Meanwhile, the spectral response of this alloy (Eg = 1.38 eV) is very consistent with the solar spectrum. We expect that our results will be helpful for the applications of optoelectronic devices.