Low-resistance ohmic contacts for microwave and lightwave devices

The fabrication of low-resistance ohmic contacts to n- and p-type compound semiconductor layers is reported. Each contact consists of a five-layer structure of evaporated metal that is alloyed at a critical temperature. Measurements of the alloyed contacts showed resistances in the 10/sup -7/- Omega -cm/sup 2/ range, which is lower than previously obtained results from conventional three-layer metallization systems produced by evaporation of an appropriate eutectic alloy. The morphology of the contacts was excellent, with good linewidth control and completely reproducible results, which makes them useful for fabricating high-speed devices with low series resistances and high cut-off frequencies. Details of the contact-formation processes are provided.<
>