InGaP/GaAs HBT's with high-speed and low-current operation fabricated using WSi/Ti as the base electrode and burying SiO/sub 2/ in the extrinsic collector

We have developed high-performance InGaP/GaAs HBT's capable of high-speed as well as low-current operation: an HBT with an emitter size S/sub E/ of 0.6/spl times/4.6 /spl mu/m exhibited f/sub T/ of 138 GHz and f/sub max/ of 275 GHz at I/sub c/ of 4 mA; and an HBT with S/sub E/ of 0.3/spl times/1.6 /spl mu/m exhibited f/sub T/ of 96 GHz and f/sub max/ of 197 GHz at I/sub c/ of 1 mA. These results are the best ever reported for GaAs-based HBT's. This high performance is due to the simultaneous reduction of S/sub E/ and C/sub BC/ by using WSi/Ti as the base electrode and by burying SiO/sub 2/ in the extrinsic collector.