Theoretical study of bismuth-doped CdTe

The electronic structure and thermodynamic properties of bismuth impurities in cadmium telluride (CdTe) are studied by means density functional theory calculations. The exchange and correlation are treated using the hybrid functional HSE, where the range-separation parameter is tuned to fit the CdTe band gap. The spin-orbit coupling is included in the calculations, showing a strong effect on the Bi-related energy levels. The band diagram and the formation energies are obtained for substitutional and interstitial configurations. It is shown that simple substitutional impurities can generate in-gap bands, which can act as intermediate levels in two-photon absorption and can be appropriate for intermediate-band solar cells.