Investigating the use of HSE Hybrid Functionals to Improve Electron Transport Calculations in Si, Ge, Diamond, and SiC

In this work, we employ density functional theory with HSE hybrid functionals (HFs) to calculate the electronic band structure of Si, Ge, diamond, and SiC in an attempt to improve upon electron-phonon scattering rates calculated with conventional PBE exchange-correlation functionals. To check for possible improvements, the band structure of each material calculated with the PBE functional is compared to that obtained with HSE HFs. The first point of comparison is the effective electron mass at the conduction band (CB) minimum. These values are calculated and compared to experimental data. In addition, the joint density of states (JDOS) is calculated for each material. Peaks and shoulders in the JDOS plot (representing transition energies at symmetry points in the band structure) are compared to the values obtained experimentally. The results show that there is no consistent improvement in the calculated effective masses or symmetry point locations from PBE to HSE, suggesting a ‘compression’ of the CB that may affect the calculated electron-phonon scattering rates.