Defect calculations in Ga-based semiconductors using optimal hybrid functionals

• Applicant: Professor Dr. Thomas Frauenheim
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2018 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 394149042

• Final Report Year: 2022

Final Report Abstract

The work in the project has verified our starting assumption, that tuning the two parameters of HSE-type hybrid functionals till the proper piecewise linear behavior of the total energy, as a function of occupation numbers, is achieved, allows for accurate prediction of defect properties in semiconductor crystals. Using such optimized functionals we have obtained and published important data for defects in Ga-based semiconductors, including GaN (used in blue LEDs), Ga2O3 (a new semiconductor used in power electronics), and the Ga-based chalcopyrites, CuGaS2, CuGaSe2 (which are materials of thin film solar cells). The observed trends in materials specific optimal parameters have helped us to develop a new exact exchange (non-hybrid) functional with improved electronic screening, which is transferable upon changing the cation or the anion of a compound semiconductor, and allows to treat various alloy compositions with the same functional. We have also investigated layered materials (h-BN and GaSe) and found that the effect of inhomogeneous electronic screening near an interface diminishes the accuracy of defect results. We have suggested the improvement of our new functional to account for that, and submitted our proposal to the DFG for funding.

Publications

• Carbon in GaN: Calculations with an optimized hybrid functional. Physical Review B, 99(8).
  Deák, Peter; Lorke, Michael; Aradi, Bálint & Frauenheim, Thomas
  
• Defect calculations with hybrid functionals in layered compounds and in slab models. Physical Review B, 100(23).
  Deák, Peter; Khorasani, Elham; Lorke, Michael; Farzalipour-Tabriz, Meisam; Aradi, Bálint & Frauenheim, Thomas
  
• Optimized hybrid functionals for defect calculations in semiconductors. Journal of Applied Physics, 126(13).
  Deák, Peter; Lorke, Michael; Aradi, Bálint & Frauenheim, Thomas
  
• Intrinsic defects of GaSe. Journal of Physics: Condensed Matter, 32(28), 285503.
  Deák, Peter; Han, Miaomiao; Lorke, Michael; Tabriz, Meisam Farzalipour & Frauenheim, Thomas
  
• Koopmans-compliant screened exchange potential with correct asymptotic behavior for semiconductors. Physical Review B, 102(23).
  Lorke, Michael; Deák, Peter & Frauenheim, Thomas