Berlin 2024 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 7: Transport properties I
HL 7.2: Talk
Monday, March 18, 2024, 15:15–15:30, ER 325
Stoichiometry fluctuations and geometrical confinement in random alloys: a case study on SiGe:C — •Daniel Dick1,2,3, Florian Fuchs1,2,3, Jörg Schuster1,2,3, and Sibylle Gemming3,4 — 1Center for Microtechnologies, Chemnitz University of Technology, Chemnitz, Germany — 2Fraunhofer Insitute for Electronic Nano Systems (ENAS), Chemnitz, Germany — 3Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, Chemnitz, Germany — 4Institute of Physics, Chemnitz University of Technology, Chemnitz, Germany
We investigate the effect of base layer scaling in silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) and evaluate the effect of local fluctuations in atomic concentrations using electronic structure theory.
For calculating the band structure of SiGe:C alloy with varying Ge and C content we present a new parameterization of Germanium in the framework of extended Hückel theory (EHT). Combined with the use of empirical potentials for structural relaxation, it enables us to efficiently simulate a large number of permutations of the atomic structure to quantify the influence of atomic-scale fluctuations on the electronic structure and transport properties using unit cells with more than a hundred atoms.
Comparing bulk SiGe:C alloy and thin layers gives insight on how quantum confinement and local stoichiometry fluctuations affect transport properties of ultra-scaled HBTs. Results are verified by first-principles calculations using density functional theory.
Keywords: silicon germanium; random alloy; stoichiometry fluctuations; electronic structure theory; extended hückel theory