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 mA/mm 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.