Improvement of Ge/Pd/GaAs ohmic contact by In layer

Abstract

The presented work describes behaviour of contact structures of the Ge/Pd type with the In layer deposited on the surface of the GaAs substrate plate prior to the metallization. The most suitable structure by contact resistivity and thermal stability is Ge(40 nm)/Pd(20 nm)/In(22 nm). This structure shows minimal contact resistivity 2 × 10⁻⁶ Ωcm². Raman spectroscopy and XPS spectroscopy was used for the contact structure analysis. After thermal annealing, the metallization contains GePd phase and a thin germanium layer remains at the surface. Very slight reaction of indium with the substrate (creation of a ternary phase InGaAs) has been proved. Germanium and palladium diffuse into the GaAs substrate, the surface layer of GaAs is doped by Ge and Pd is built in the GaAs crystal structure instead of arsenic.