Regensburg 2010 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 36: Ge, GeSi, and Si

HL 36.5: Vortrag

Mittwoch, 24. März 2010, 10:30–10:45, H14

First Principles Study of the Oxide at the Ge-GeO₂ Interface — •Jan Felix Binder, Peter Broqvist, and Alfredo Pasquarello — Ecole Polytechnique Fédérale de Lausanne (EPFL), Institute of Theoretical Physics, CH-1015, Switzerland

As Si-based metal-oxide-semiconductor devices are approaching their technological and physical limits due to aggressive scaling, the search for new material solutions intensifies. Germanium shows high electron and hole mobilities together with a small electronic band gap, and is seriously being considered as a viable alternative to silicon. However, current stateof-the-art germanium-insulator interfaces show excessively high defect densities compared to conventional silicon/insulator interfaces. Hence, the characterization of both the structural and electronic properties of the Ge/GeO₂ interface is highly relevant. We study germanium suboxides within a density functional approach focusing on their energetic, atomic, and electronic properties. First, we calculate penalty energies of germanium suboxides, and find significantly smaller values than for silicon. This supports a higher concentration of suboxides at Ge/GeO₂ interfaces. Second, we generate amorphous models of GeO and GeO₂ through ab initio molecular dynamics and study their structural and electronic properties. The analysis of the electronic structure of GeO reveals the occurrence of suboxide states in the lower part of the band gap of GeO₂ consistent with several experimental observations at Ge/GeO_x interfaces.