Alloying Behavior and Reliabilty of Pt Embedded Metal/n+-GaAs Thin Ohmic Contact System


Pt embedded ohmic contacts to n+-GaAs (AuGe-800 Å/ Ni-150 Å/Pt-200 Å/Au-500 Å and AuGe-800 Å/Pt-200 Å/Ni-150 Å/Au-500 Å/n+-GaAs) have been developed for the advanced discrete devices and MMIC (monolithic microwave integrated circuit) applications. The specific contact resistance investigated by Transmission Line Method is 1x10-6 Ω cm2. Ohmic contact reliability investigated by thermal storage test at 300 °C under N2 ambient demonstrated nearly the same contact characteristics after 3000 hours. In both systems, X-ray diffraction results and Auger depth profiles show that the good ohmic contact is related to the formation of Au7Ga2, PtAs2, and Ni19Gen12 phases. AuGa compound enhances the creation of Ga vacancies, allowing incorporation of Ge into Ga sites, and PtAs compound is piled up in the middle of AuGa layer to suppress As outdifrusion from GaAs substrate. TEM cross-sectional view indicates that metal/n+-GaAs reaction layer is ∼ 1200 Å beneath GaAs. Surface and interface are very smooth and abrupt in comparison to conventional AuGe/Ni/Au contact.

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Kim, C.Y., Lee, W.S., Kwon, H.J. et al. Alloying Behavior and Reliabilty of Pt Embedded Metal/n+-GaAs Thin Ohmic Contact System. MRS Online Proceedings Library 448, 389–394 (1996).

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