High performance 0.25 μm non-recessed self-aligned Gate GaAs P-HEMT with improved yield and uniformity

This paper describes a high performance 0.25 μm non-recessed self-aligned gate (SAG) GaAs P-HEMT which aims at improving the device yield and uniformity. In order to eliminate the critical gate recess etching process, the non-recessed gate structure was employed with thin (50 Å) n ⁺-cap epitaxial layer. The possible performance degradations of the non-recessed gate device could be minimized through the newly developed SAG process with thermally stable Mo-barrier gate metal and Pd/Ge-based thin ohmic contact. In spite of the non-recessed gate structure, the optimized device showed excellent DC and RF characteristics with average g _m,max=395 mS/mm, f _T=75 GHz and f _max=190 GHz, and the device yield and uniformity were improved considerably.