Submicrometer n⁺-Ge Gate AlGaAs/GaAs MISFET's

Submicrometer n⁺-Ge gate AlGaAs/GaAs M1SFET's have been developed by designing a fabrication process for the n⁺ - implanted region. The short-channel effect was sufficiently suppressed by lowering ion-implantation energy down to 50 keV to achieve a standard deviation of threshold voltage as small as 13 mV for 0.5-μm-gate FET's in a 2-in-diameter wafer. The source resistance was reduced by increasing the annealing temperature to 850°C to obtain a transconductance of 500 mS/mm for a 0.5-μm-gate FET. Even after annealing at such a high temperature, the quality of the channel layer was maintained at a sufficient level to realize a large cuttoff frequency of 70 GHz for a 0.4-μm-gate FET. A divide-by-four static frequency divider was also fabricated using the above-mentioned fabrication technology. Successful operation at 16 GHz at 300 K was obtained with a divider employing 0.9-μm-gate FET's at a low power dissipation of 36 mW per T-flip-flop.