Regensburg 2010 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 61: Poster II: Materials, Interfaces and Heterostructures

HL 61.4: Poster

Donnerstag, 25. März 2010, 18:00–20:00, Poster D1

Ba_0.7Sr_0.3O thin films on n-Si as high-k material: correlation between structural and electrical properties — •Lisa Kühnemund¹, Dirk Müller-Sajak¹, Alexandr Cosceev², Herbert Pfnür¹, and Karl R. Hofmann² — ¹Leibniz-Universität Hannover, Inst. f. Festkörperphysik — ²Leibniz-Universität Hannover, Bauelemente der Mikro- und Nanoelektronik

Crystalline and perfectly lattice matched Ba_0.7Sr_0.3O films were grown on Si(001), which have a dielectric constant of є_r≈28. The thin films have a perfect atomically sharp interface, as found by XPS. They were grown in a UHV chamber by MBE in oxygen ambient conditions and capped with 100nm Au for ex-situ electrical measurements. A 0.5-2ML thick Al intermediate layer improves the adhesion between the Au and the oxide, which have an influence on the electrical properties depending on the thickness of the Al layer.

This material has attractive electrical properties: XPS measurements at the interface show no evidence for SiO₂ formation. Furthermore the density of states at the interface (determined by the Terman method) is very low (6.3·10¹⁰eV⁻¹cm⁻²) and a factor 10-100 lower than for amorphous BaO, SrO and Ba_0.7Sr_0.3O. This is caused by the good structural properties of the crystalline oxide. Low leakage current densities (10⁻⁶A/cm²) have been found by current-voltage (IV) measurements, supported by sufficient valence and conduction band offsets 1eV at the semiconductor/insulator interface, as measured with XPS and EELS. These band offsets can be tuned by varying the conditions during growth of the interface.