Ohmic Contacts to n-type GaAs Using GeMoW Metallizati1on for Self-aliged Processing

We have formed GeMoW and Ge(As)MoW ohmic contacts to n-type GaAs using different types of annealing techniques, under either a forming gas or an As overpressure. A comprehensive study of both contacts is presented using electrical testing, Auger electron spectroscopy, secondary ion-mass spectrometry, transmission electron microscopy and scanning transmission electron microscopy. Very low specific contact resistivities, in the range of a few 10-7 ?cm 2 , have been obtained, when the contact included an As doped Ge layer with a doping level of 10 20 cm ?3 and was annealed using the semi-closed box technique under an As overpressure.