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MM: Fachverband Metall- und Materialphysik
MM 18: Poster Session I
MM 18.12: Poster
Montag, 16. März 2020, 18:15–20:00, P4
Electronic structure and stability studies on random configurations of silicon-germanium carbon alloys — •Willi Roscher1, Florian Fuchs2,3,4, Christian Wagner5, Jörg Schuster2,3,4, and Sibylle Gemming4,5 — 1Leibniz Institute for Solid State and Materials Research Dresden, D-01069 — 2Fraunhofer Institute for Electronic Nano Systems, D-09126 — 3Center for Microtechnologies, Technische Universität Chemnitz, D-09126 — 4Institute of Physics, Technische Universität Chemnitz, D-09126 — 5Helmholtz-Zentrum Dresden-Rossendorf, D-01328
One important application of silicon-germanium carbon are heterojunction-bipolar transistors (HBTs). Current research aims to reduce the device dimensions, making fluctuations on the atomic scale a serious concern. We therefore study the statistical distributions of the electronic properties in bulk Si1−x−yGexCy. The entire composition range 0 ≤ x ≤ 1 including small carbon concentrations is considered. Density functional theory is used in this study.
We demonstrate fluctuations of the band gap, which are in the range of about 10 %. These fluctuations occur in bulk SiGeC on a local scale, and they will become observable in down-scaled devices. Further properties, such as the lattice constant, the formation energy, and the change of Gibbs free energy are studied as well. Entropic contributions decrease the Gibbs free energy of mixed systems, which stabilize SiGeC at room temperature. Finally, local changes of the band gap in an HBT due to a spatially varying germanium concentration are presented.