Correlation of interface composition and barrier height for model AuGeNi contacts to GaAs

Model contacts to GaAs that include nonalloyed layered structures of Au, Ge, and Ni in various combinations are used to establish a correlation between interface composition and large changes in barrier height φB. The interface Fermi level EiF and chemistry during initial contact formation were inve...

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Veröffentlicht in:Applied physics letters 1987-02, Vol.50 (5), p.250-252
Hauptverfasser: WALDROP, J. R, GRANT, R. W
Format: Artikel
Sprache:eng
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Zusammenfassung:Model contacts to GaAs that include nonalloyed layered structures of Au, Ge, and Ni in various combinations are used to establish a correlation between interface composition and large changes in barrier height φB. The interface Fermi level EiF and chemistry during initial contact formation were investigated by x-ray photoemission spectroscopy; the corresponding φB for the thick contact was obtained by current-voltage (I-V) measurement. The circumstances under which a thin (∼10 Å) Ge layer at the GaAs interface can produce φB =∼0.25–0.4 eV (as measured by I-V) are described. For all model contacts examined a φB range from ∼0.25 to 0.9 eV is observed. This result questions the usual assumption of a relatively fixed φB of ∼0.8 eV for the alloyed AuGeNi contact and offers an alternative explanation for the mechanism of ohmic contact formation. The conditions that define the exceptionally low φB contacts provide a guide for the design of nonalloyed tunnel ohmic contacts.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.98215