Reduction of the short-channel effects for GaAs MESFETs by double shallow n/sup +/-layers

In order to suppress the short-channel effects of subquarter-micrometer gate-length GaAs MESFETs, it is necessary to fabricate shallow n/sup +/ layers without any increase of parasitic resistance. To advance this line of research, a double shallow n/sup +/-layer structure was investigated using a T-shaped resist mask and oblique ion implantation. Employing this shallow n/sup +/-layer structure, the threshold-voltage shift was suppressed and the subthreshold characteristics were improved for subquarter-micrometer gate-length FETs. A transconductance of 500 mS/mm for the 0.15- mu m gate-length FET and a cutoff frequency of 33 GHz for the 0.35- mu m gate-length FET were obtained.>