Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 77: Oxides and insulators: Epitaxy and growth
O 77.4: Talk
Thursday, March 25, 2010, 15:45–16:00, H42
MOS diodes with BaO, SrO and Ba0.7Sr0.3O thin films on Si(001) as a high-k dielectric — •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
We have grown BaO, SrO and Ba0.7Sr0.3O films on clean Si(001) in order to find a new high-k gate oxide. These films are highly hygroscopic
and have to be sealed completely by the metal gate electrode in order to perform ex-situ electrical measurements.
We show that complete wetting of a Au layer can be obtained
by introducing a thin layer (0.5-1ML) of Al after the oxide growth.
All three oxides have remarkable electrical properties: Dielectric constants near the values for volume
material were obtained. Low leakage
current densities (10−6A/cm2 for Ba0.7Sr0.3O) have been measured. These results are
supported by band offsets measured on
the unstructured oxides by XPS and EELS (all above 1eV).
Changing the growth conditions at the interface cause a shift in the band offsets induced by states
at the interface.
Growth of crystalline and lattice matched Ba0.7Sr0.3O turns out to be superior to the amorphous
layers of BaO and SrO in terms of defect densities at the interface and of leakage currents.
We observed the lowest density of states at the interface
of 6.3·1010eV−1cm−2 by the Terman method and typically two orders of magnitude lower
leakage currents for the crystalline oxide. Structural and chemical reasons will we discussed.