Modeling charged defects and defect levels in semiconductors and oxides with density functional theory – an improved, inside-out perspective
Event details
| Date | 17.10.2016 |
| Hour | 14:30 › 15:30 |
| Speaker |
Peter A. Schultz, Sandia National Laboratories, Albuquerque, New Mexico, USA. Bio : Dr. Peter A. Schultz is a Principal Member of Technical Staff at Sandia National Laboratories in the Multiscale Science Department. Since 2008, he has served as an Executive Editor for Modeling and Simulation in Material Science and Engineering (MSMSE), appointed as co-Editor-in-Chief in 2016. His research since he arrived at Sandia in 1992 has focused on the development of multiscale materials modeling methods requiring high-performance computing. He is the principal developer of the SeqQuest code (http://dft.sandia.gov/Quest/), a parallel local-basis DFT pseudopotential code, used as a computational platform to enable large-scale simulations of defect physics and materials chemistry, particularly emphasizing applications in radiation effects in electronics. |
| Location | |
| Category | Conferences - Seminars |
Abstract : The fundamental band gap defines a semiconductor, and defects in semiconductors—when intentional, called dopants, when not, impurities and lattice imperfections—introduce electron and hole traps within the gap that modify the performance of an electronic device. Density functional theory (DFT) has emerged as an important tool to probe microscopic processes in materials and particularly defects in semiconductors. However, the conventional DFT band gap is often half or less of the experimental band gap, widely known as the DFT “band gap problem”. As the band gap defines the relevant energy scale for defect levels, this appears to preclude DFT for quantitative studies for charged defects that underlie much of the defect chemistry governing interesting semiconductor behavior. Implementing a method incorporating rigorous boundary conditions for net charge in supercells, I find that a ‘defect band gap’, the computed range of energies accessible to localized defect charge transitions, is mostly insensitive to the size of the crystal Kohn-Sham gap. Moreover, the computed defect band gap agrees well with experimental band gap for many semiconductors and insulators. This provides insight into the DFT ‘band gap problem’, but also defines and validates best practices for modeling and simulation. With validated accuracy in defect level predictions across the full experimental band gap, this demonstrates conventional DFT can be used for quantitative basic research into ionic and covalent materials. --- Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000
Practical information
- Expert
- Free
- This event is internal
Organizer
- LAMMM
Contact
- Géraldine Palaj