| AVS 54th International Symposium | |
| Surface Science | Thursday Sessions |
| Session SS2-ThM |
| Session: | Surface Structure of Compound Semiconductors |
| Presenter: | J. Shen, University of California, San Diego |
| Authors: | J. Shen, University of California, San Diego D.L. Winn, University of California, San Diego A.C. Kummel, University of California, San Diego |
| Correspondent: | Click to Email |
The key to fabricating a III-V MOSFET is forming an electrically passive oxide-semiconductor interface. In an effort to identify an unpinned oxide/semiconductor interface on InAs, a detailed study of In2O adsorbed to InAs(001)-c(8x2)/(4x2) was performed. Scanning tunneling microscopy (STM) and density functional theory (DFT) were used to ascertaining how In2O adsorbates bond to the clean InAs(001)-c(8x2)/(4x2) surface. The InAs(001)-c(8x2)/(4x2) surface consists of a top row of In atoms which are bonded to tricoordinated As atoms containing partially filled dangling bonds. STM results showed that the initial In2O molecules only occupy specific sites at the edge of the rows. These In2O atoms most likely form new In-As bonds to the surface. This is a favorable bonding structure for oxide/semiconductor interfaces since it avoids As-O bond formation which is likely to create states in the band gap. In addition, the formation of In-As bonds restores the tricoordinated As atoms to a more bulk-like bonding environment. A height analysis was performed to determine growth mechanism. At low coverage (20% monolayer), the In2O adsorbates formed islands that are elongated in the [110] direction. Prior to all the first layer sites being occupied with In2O molecules, second layer growth was observed on the islands. Each layer of oxide has a distinct height, however, the second and subsequent layers appear to be amorphous. In addition, the effect of annealing In2O/InAs(001)-c(8x2)/(4x2) was studied. The annealed samples were more ordered and uniform. The oxide molecules on the annealed samples filled in the troughs and formed ordered islands with rows in [i10] direction. Comparisons of oxide height distributions before and after annealing, show the oxide height is reduced from 1.5 Å to 1 Å. This is consistent with the In-In bond formation between two nearest neighbor In2O atoms in the [i10] direction. Most importantly, for both room temperature deposition and annealing, the clean surfaces lattice is left unperturbed, the In2O adsorbates never cause the abstraction of any surface atoms on the InAs(001)-c(8x2)/(4x2) surface and the In2O molecules only occupied specific sites. The formation of an ordered oxide-interface without disruption of the InAs(100)-c(8x2)/(4x2) lattice is favorable for creating an unpinned oxide-semiconductor interface.