Improved DC and RF performance in Si/SiGe n-MODFETs with ion-implanted buried p-well doping

The dc and RF characteristics of Si/SiGe n-MODFETs with buried p-well doping incorporated by ion implantation are reported. At a drain-to-source biasV(ds) of +1 V devices with 140-nm gate length had peak transconductance g(m) of 450 mS/mm, and maximum dc voltage gain A(v) of 20. These devices also had "off-state" drain current I-off of 0.15 mA/mm at V-g = -0.5 V. Control devices without p-well doping had A(v) = 8.1 and I-off = 13 mAlmm under the same bias conditions. MODFETs with p-well doping had f(T) as high as 72 GHz at V-ds = +1.2 V. These devices also achieved f(T) of 30 GHz at a drain current, I-d, of only 9.8 mA/mm, compared to I-d = 30 mA/mm for previously published MODFETs with no p-well doping and similar peak f(T).