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 biasVds of +1 V devices with 140-nm gate length had peak transconductance gm of 450 mS/mm, and maximum dc voltage gain Av of 20. These devices also had "off-state" drain current Ioff of 0.15 mA/mm at Vg = -0.5 V. Control devices without p-well doping had Av = 8.1 and Ioff = 13 mA/mm under the same bias conditions. MODFETs with p-well doping had fT as high as 72 GHz at Vds = +1.2 V. These devices also achieved fT of 30 GHz at a drain current, Id, of only 9.8 mA/mm, compared to Id = 30 mA/mm for previously published MODFETs with no p-well doping and similar peak fT. © 2005 IEEE.