High f/sub /spl tau// and f/sub max/ InAlAs-InGaAs transferred-substrate HBTs

We report the design, fabrication and measurement of a high speed InAlAs-InGaAs heterostructure bipolar transistor (HBT). At a V/sub CE/ of 0.96 V the current gain cut-off frequency, f/sub /spl tau//, and the maximum oscillation frequency, f/sub max/, were 300 GHz and 235 GHz, respectively. This value of f/sub /spl tau// is the highest ever reported for bipolar transistors. At a slightly higher V/sub CE/ bias, simultaneously high values of f/sub /spl tau//=293 GHz and f/sub max/=275 GHz were obtained. Fast HBTs have become key components in future and current designs for 100 GHz digital communication systems, direct digital frequency synthesizers and radar. To achieve these goals, it is essential for the device to have simultaneous high values of f/sub /spl tau// and f/sub max/ capability for high current density operation and a low extrinsic base collector capacitance.