Toward THz Transistor: Pseudomorphic Heterojunction Bipolar Transistors (PHBT)

Terahertz (THz) communication systems require the development of ultra-fast transistor technologies for VCO sources with power amplification (>50 mW) and low noise receiver (NF<8 dB). InP-based HBTs are the most promising technology for achieving THz operation based on the current gain cutoff frequency versus breakdown voltage trend for various transistor technologies and material systems. It is the only known transistor technology can deliver THz bandwidth with output breakdown voltage greater than IV, hence, a potential higher power transistor amplifier can be realized. This paper proposes and experimentally demonstrates that pseudomorphically grading the collector of an SHBT shows an increase in device speed. High frequency measurements were performed at room temperature using an off-wafer short-open-load-through (SOLT) calibration on an HP8510C vector network analyzer (VNA) from DC to 50 GHz.