AVS 50th International Symposium
    High-k Gate Dielectrics and Devices Topical Conference Tuesday Sessions
       Session DI-TuA

Paper DI-TuA10
Band Offsets at Ba- SrTiO@sub 3@ / Si Interfaces

Tuesday, November 4, 2003, 5:00 pm, Room 317

Session: High-k Dielectric Characterization
Presenter: F. Amy, Princeton University
Authors: F. Amy, Princeton University
A. Wan, Princeton University
A. Kahn, Princeton University
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The continuous drive toward faster electronics and scaling down of MOSFET device dimensions requires alternatives to SiO@sub 2@ for gate dielectrics. High-k dielectrics have therefore received considerable attention from industry and the scientific community. Crystalline perovstike oxides such as SrTiO@sub 3@ and BaTiO@sub 3@ are of special interest and offer several advantages. First, they can be MBE-grown lattice-matched to Si (or Ge) substrates with very low interface state density.@footnote 1@ Second, they can serve as a buffer layer for the growth of semiconductors, opening possibilities for integrating Si electronics and III-V optoelectronics. However, several issues concerning these materials remain to be fully addressed, among which band offsets with Si and other semiconductors. In this work, we use a SrTiO@sub 3@(100 Å)/BaSrO(11 Å)/Si structure grown by MBE, and X-ray and UV photoemission spectroscopy to study core levels and valence band respectively. Depending on surface preparation, including ex-situ UV ozone, O@sub 2@ or UHV annealing, the valence band maximum position shifts by more than 2 eV, whereas very little if any shift is observed on core levels. These findings indicate that surface composition and morphology are of paramount importance in the UPS determination of electronic structure, and may explain discrepancies between results reported in the literature. Our investigation of clean and stoichiometric SrTiO@sub 3@ surface indicates that its conduction band minimum is located 0.4 eV (± 0.4) below the one of silicon. An in-depth investigation of the role of surface preparation is being pursued, and results on BaTiO@sub 3@/SrTiO@sub 3@/Si samples will be reported. @FootnoteText@ @footnote 1@ . R. A. McKee, F. J. Walker, and M. F. Chisholm, Phys. Rev. Lett. 293, 468 (2001)