Alloying behaviour of Au-Ge/Pt ohmic contacts to GaAs by pulsed electron beam and furnace heating

Au-Ge/Pt contacts on n-type GaAs have been irradiated by a pulsed electron beam to yield excellent ohmic behaviour. Auger electron spectroscopy (a.e.s.) measurements of the depth profiles of the constituent elements in these irradiated contacts indicate that considerable intermixing of the metals with Ga and/or As is not necessary for good ohmic behaviour. Subsequent isochronal (2 min) furnace heating in H2 of these contacts at different temperatures shows that the Au-Ge/Pt metallisation system is highly reactive, with the inter mixing and the ohmic behaviour being a strong function of the furnace temperature. From a.e.s. measurements the important role of Ge as a dopant in generating a heavily doped GaAs layer at the metal-GaAs interface responsible for the ohmic character of the contacts is confirmed. Low specific contact resistance is closely related to the ability in incorporating Ge in a shallow GaAs layer during the alloy cycle.