AVS 53rd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM-ThP

Paper EM-ThP15
Electronic Properties of Adsorbates on GaAs(001)-c(2x8)/(2x4)

Thursday, November 16, 2006, 5:30 pm, Room 3rd Floor Lobby

Session: Electronic Materials and Processing Poster Session
Presenter: D.L. Winn, University of California, San Diego
Authors: D.L. Winn, University of California, San Diego
M.J. Hale, University of California, San Diego
A.C. Kummel, University of California, San Diego
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The key issue in fabricating a III-V MOSFET is forming an unpinned interface between the gate oxide and the semiconductor. A systematic experimental and theoretical study has been performed to determine the causes of oxide pinning and unpinning on GaAs(100). Scanning tunneling spectroscopy (STS) and density functional theory (DFT) were used to study four different adsorbates (O@sub 2@, Ga@sub 2@O, In@sub 2@O, and SiO) bonding to the GaAs(001)-c(2x8)/(2x4) surface. The STS results revealed that out of the four adsorbates only one left the Fermi level unpinned, Ga@sub 2@O. DFT calculations were used to elucidate the causes of the Fermi level pinning. Two distinct pinning mechanism were identified: direct (the adsorbate induced states in the band gap region) and/or indirectly pinning (generation of undimerized As atoms). In the cause of O@sub 2@ adsorbing onto GaAs the Fermi level pinning was found to result only from indirect case, while, In@sub 2@O was shown to pin the Fermi level directly. SiO however, was found to exhibit both indirect and direct (build-up of local charge, and formation of partially filled dangling bonds on some of the Si atoms) Fermi level pinning. The close correlation between experiment and theory suggest that DFT can be used to predict oxide pinning and unpinning on III-V semiconductors.