GaAs - MESFETs with highly doped (1018cm-3) channels - An experimental and numerical investigation

GaAs MESFETs with both micron and submicron gates were fabricated and evaluated. FETs with 1 .2µm gate show an extrinsic transconductance of 225mS/mm at V, cut-off frequencies around 2OGHz and a noise figure of 2dB at 8GHz with 9dB associated gain. Breakdown voltage is higher than 6V. FETs with 1.2µm and 0.4µm gates were simultaneously fabricated on the same wafer to investigate short channel effects. The short channel devices show a good saturation behaviour and no shift in the threshold voltage compared to the long channel devices thus demonstrating a pronounced alleviation of short channel effects. The dependence of device performance with micron and submicron gates upon doping concentration is investigated by detailed computer simulations. Good agreement between theoretical and experimental results is obtained.