AVS 47th International Symposium
    Electronics Tuesday Sessions
       Session EL-TuP

Paper EL-TuP4
Work Function and Barrier Height Correlation for Al/GaAs Schottky Contacts Modified by Ultra-Thin, Doped Si and Ge Interlayers

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: T.A.R. Müller, University of Minnesota
Authors: T.A.R. Müller, University of Minnesota
M.I. Nathan, University of Minnesota
A. Franciosi, University of Minnesota and Universita' di Trieste
C.J. Palmstrom, University of Minnesota
Correspondent: Click to Email
A promising alternative to alloyed contacts to GaAs, which suffer from lateral diffusion and spiking problems, is the deposition of ultra-thin (<2ML) Si-films on GaAs prior to contact formation with the metal. It has been shown@footnote 1,2@ that these engineered interfaces can be used to increase or decrease the barrier height of Al to n-GaAs, depending on whether the Si is co-deposited with a group-III or group-V element, respectively. Although the cause for this change in barrier height is still unclear, it has been proposed that the formation of dipoles at the interface is responsible for the change in barrier height,@footnote 1@ where the orientation of the dipoles is determined by whether Si bonds to a group-III or group-V element at the GaAs surface. In principle, the magnitude of the dipoles is sensitive to the interface chemistry and composition. In-situ work function measurements performed at different stages of growth of Si/GaAs and Ge/GaAs layers will be presented and related to electrical measurements of the barrier height after subsequent deposition of Al used to form the Schottky contact. In the Si/GaAs system, we find that, compared to the work function of the GaAs(001)c(4x4) starting surface, the co-deposition of Si with Al leads to a sharp decrease in the work function by 0.3eV with a corresponding increase in the barrier height to >1eV, while the co-deposition of Si with As shows an increase in the work function of 0.2eV for a Si-coverage of 0.5ML. The corresponding barrier height lies in the 0.2eV range. In this talk, we report a systematic study of the effect of Ge interlayers (<4ML) on the barrier height and compare the data to barrier heights observed for similar Si interlayer thicknesses. @FootnoteText@ @footnote 1@ M. Cantile et al, Appl. Phys. Lett. 64 (1994), 988 @footnote 2@ S. De Franceschi et al, Appl. Phys. Lett. 72 (1998), 1996.