Ultrafast transferred-substrate heterojunction bi-polar transistor ICs for high-speed fiber-optic transmission

Summary form only given. Heterojunction bipolar transistors (HBTs) are used in Gbit/s fiber-optic ICs, GHz analog-digital converters and microwave PLLs. For 50-GHz clock rates and beyond, transistor bandwidths of several hundred GHz are required. Increased bandwidths in CMOS VLSI and III-V high electron mobility field effect transistors (HEMTs) have been achieved by scaling device lithographic dimensions. In contrast, conventional double mesa HBT bandwidth has not increased with reduced lithographic dimensions due to non-scalable collector-base capacitance. We have developed a transferred substrate HBT process, with significant changes to the device structure that render the device scalable. The process also has significant potential advantages in low parasitic wiring environment, microstrip ground plane, low thermal impedance for high-power operation and increased packing density. HBTs with f/sub max/ >400 GHz have been demonstrated and 50-GHz bandwidth feedback amplifiers have been fabricated. Some medium scale ICs like decision circuits, multiplexer/demultiplexer circuits and variable gain amplifiers are currently under development. Target applications include 100-Gbit/s fiber transmission, microwave analog-digital converters and mm-wave frequency synthesis.