Improved uniformity of contact resistance in GaAs MESFET using Pd/Ge/Ti/Au ohmic contacts

Improved contact resistance uniformity, with a low resistance on high-low doped GaAs MESFET, was demonstrated using a Pd/Ge/Ti/Au ohmic contact. The lowest contact resistivity obtained was 2.8/spl times/10/sup -6/ /spl Omega/-cm/sup 2/. The average value and standard deviation (/spl Delta/Rc) of the contact resistance (Rc) were 0.73 and 0.07 /spl Omega/-mm, respectively, which were more uniform than those for AuGe/Ni contacts with an average Rc of 0.77 /spl Omega/-mm and /spl Delta/Rc of 0.16 /spl Omega/-mm. The improved uniformity was attributed to the uniform penetration of the ohmic junction into the buried high-doped channel layer by solid-state reactions, resulting in the improved uniformity of device performance.