A high-speed static frequency divider employing n+-Ge gate AlGaAs/GaAs MISFETs

The high-speed potential of n⁺-Ge gate AlGaAs/GaAs MISFETs has been demonstrated by fabricating a divide-by-four static frequency divider. The transconductance of a MISFET with 0.6 µm gate length was 470 mS/mm. The small Vthstandard deviation of 13 mV throughout the 2-inch wafer confirms the principal advantage of the MISFET, namely high Vthuniformity. The frequency divider circuit was based on SCFL with 0.9 µm gate-length MISFET. A maximum toggle frequency as high as 16 GHz with a power dissipation of 36 mW per T-F/F has been achieved at room temperature. In addition, a cutoff frequency as high as 54 GHz has been achieved in a 0.5 µm gate length MISFET, which leads to an electron velocity in the channel as high as 1.7×10⁷cm/s.