Low-voltage, high-speed AlSb/InAs HEMTs

We report on the improved low-voltage, high-speed performance of AlSb/InAs HEMTs obtained using variations in doping method and layer design. Unintentionally-doped HEMTs with a 0.6 /spl mu/m gate length have a transconductance of 1 S/mm at V/sub DS/=0.4 V. After removal of the gate bonding pad capacitance from an equivalent circuit, an f/sub T/L/sub g/ product of 38 GHz-/spl mu/m is obtained at V/sub DS/=0.4 V. 0.5 /spl mu/m gate-length HEMTs that have Si doping in a very thin (9 /spl Aring/) InAs layer located in the upper AlSb barrier exhibit high drain current density and an f/sub T/ of 45 GHz at V/sub DS/=0.4 V. 0.1 /spl mu/m gate-length HEMTs that use an As-soak doping method exhibit an f/sub T/ of 230 GHz at V/sub DS/=0.45 V (after correction for the bonding pad capacitance), the highest value achieved thus far in this material system.