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

• Published in: Applied physics letters 1987-02, Vol.50 (5), p.250-252
• Main Authors: WALDROP, J. R, GRANT, R. W
• Format: Article
• Language: English
• Subjects: Applied sciences; Electronics; Exact sciences and technology; Interfaces; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.98215

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.