Speaker
Description
Diamond is a wide-bandgap semiconductor with exceptional physical properties, making it highly attractive for applications in power electronics, photovoltaics, nanophotonics, and quantum technologies. Its functionality is often engineered through the introduction of defects such as dopants or vacancies; however, accurate description of defect states remains challenging. Density functional theory (DFT) provides a useful starting point but underestimates band gaps and misplaces defect levels. These errors are especially pronounced for deep-level states, such as those associated with color centers (e.g. the NV center), and they propagate into subsequent predictions, including optical absorption. Many-body perturbation theory, in particular the GW approximation, offers significant improvement over DFT, but its accuracy strongly depends on the method used to evaluate dynamical screening. In practice, plasmon-pole models are often sufficient for insulators and semiconductors, while full-frequency methods are required for metals. Doped structures constitute a “middle-ground” between insulators and metals that has received little attention in GW studies, and even when addressed, clear benchmarks for methodological choices are often lacking.
To address this, we performed GW calculations of diamond-based structures containing substitutional boron and phosphorus, as well as phosphorus-vacancy and boron-vacancy-boron colour centres. In this way, we were able to analyse positions of impurity states and width of the bulk band gap in a variety of scenarios ranging from degenerate semiconductors to semiconductors with multiple deep defect states. We compared the Godby-Needs plasmon-pole model with the contour deformation technique using a variety of frequency grids. Furthermore, we investigated the effect of different treatments of dynamical screening on charged defects.
Our work highlights the trade-offs between accuracy and computational cost of different GW methods for simulating doped wide-bandgap semiconductors. Beyond numerical comparisons, it provides practical guidelines for choosing suitable methodologies when modelling systems where the physics lies between that of simple insulators and metals.
This work was supported by the project “The Energy Conversion and Storage”, funded as project No. CZ.02.01.01/00/22_008/0004617 by Programme Johannes Amos Commenius, call Excellent Research. This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic through the e-INFRA CZ (ID:90254). The access to the computational infrastructure of the OP VVV funded project CZ.02.1.01/0.0/0.0/16_019/0000765 “Research Center for Informatics“ is also gratefully acknowledged.
