NOVEL FULLY SELF-ALIGNED MESFET USING SOURCE AND DRAIN REGROWN NONALLOYED CONTACTS BY ALE

A new low temperature, nonalloyed, self-aligned FET process using regrowth technology on a patterned substrate has been demonstrated. A double delta-doped MESFET with regrown n++ source and drain contact regions using atomic layer epitaxy (ALE) were fabricated and characterized. In this novel regrowth technique, a silicide gate was embedded by molybdenum and a side wall oxide to prevent any contamination or unwanted reaction during the ALE growth. Two main features associated with our process that makes it an attractive technology for more uniform device performance across a large area wafer are: a) the refractory gate/GaAs interface is not subjected to any high temperature process, and b) nonalloyed ohmic contacts are achieved without undesirable lateral diffusion of n+ regions caused by annealing of implanted source and drain. The preliminary unoptimized device results show a transconductance of 40 mS/mm for gate length of 0.65 mum.