Low resistance pd/ge ohmic contacts to epitaxially lifted-off n-type GaAs film

A low resistance PdGe nonalloyed ohmic contact has been successfully formed to epitaxially lifted-off n-type GaAs films. The contact is made by lifting off partially metallized n-type GaAs films using the epitaxial lift-off method and bonding them to metallized Si substrates by natural intermolecular Van Der Waals forces. Low temperature sintering (200°C) of this contact results in metallurgical bonding and formation of the ohmic contact. We have measured specific contact resistances of 5 × 10⁻⁵ Ω-cm₂ which is almost half the value obtained for pure Pd contacts. Germanium forms a degenerately doped heterojunction interfacial layer to GaAs. Our experimental results show that germanium diffuses to the interface and acts as a dopant layer to n-GaAs film surface. Therefore, for epitaxially lifted-off n-type GaAs films, PdGe is a low resistance ohmic metal contact to use.