THE BACKSIDE PULSE DOPED CHANNEL HETEROSTRUCTURE FIELD-EFFECT TRANSISTOR - DESIGN, DC, AND RF PERFORMANCE

We report about a theoretical and experimental study of AlGaAs/InGaAs modulation doped field-effect transistors (MODFETs) having doped channels. On the basis of self consistent calculations we suggest design rules of where to introduce the channel doping into the channel to obtain high speed devices with high saturation currents and reasonable low noise performance. For a 0.35 mum gate length backside pulse doped channel device (BSPDC-HFET) with 120 mum gate width a maximum transconductance of 625 mS/mm and a maximum saturation current at V(GS) = +0.8 V of 720 mA/mm have been measured. The cut-off frequencies are f(T) = 80 GHz, f(max) = 195 GHz. At 18 GHz a minimum noise figure of NF = 1.1 dB with 17 dB associated gain were measured.