Determination of the optimum condition to introduce the doping in the channel of high speed doped channel AlGaAs/InGaAs HFET's

An investigation of the introduction of doping into the channel of Al/sub 0.25/Ga/sub 0.75/As/In/sub 0.2/Ga/sub 0.8/As HFETs to obtain high saturation currents and reasonable low noise performance is discussed. The device performance is experimentally compared to that of undoped channel HFETs having the same layer structure. For a 0.35- mu m gate length backside doped channel HFET a maximum transconductance of 625 mS/mm, a maximum saturation current at V/sub Gs/=+0.8 V of 720 mA/mm, a power gain cutoff frequency of 195 GHz, and at 18 GHz a noise figure of 1.1 dB with 17 dB associated gain were measured. >