SEM alloyed AuGeNi ohmic contacts to GaAs

A scanned electron beam from a commercial SEM is used for the localized alloying of vacuum evaporated AuGeNi contacts on n-type GaAs. The contact quality is studied for metallization thickness, 450–1350 Å, for furnace and electron beam alloyed contacts. For the electron beam alloyed method, the contact resistivity decreases with increasing metallization thickness and remains constant for thicknesses above 750 Å. Scanning electron microscopy and electron microprobe analysis shows that electron beam alloyed contacts undergo less redistribution of contact constituents than furnace alloyed contacts. The stability of the contacts is determined by high temperature ageing.