| PhD Viva

Name of the Speaker: Soumya Ranjan Panda (EE20D850)
Guide: Dr. Anjan Chakravorty
Online meeting link: https://u-bordeaux-fr.zoom.us/j/82110613169
Date/Time: 19th September 2022, 5 PM
Title: Investigating High-Frequency SiGe HBTs: Assessment of Characterization and New Architecture Exploration

Abstract

Silicon germanium heterojunction bipolar transistors (SiGe HBTs) are rapidly evolving to cater the increased functionality and speed demands of the modern communication systems (4G, 5G & upcoming 6G). With the emerging mm-wave and THz market, the precise characterization and modeling of the devices are crucial to optimize the circuit-performance and minimize the number of overall design cycles. In this work, a very high frequency (up to 500 GHz) measurement is carried out and corresponding data is analyzed using two finite element tools, one solving the EM equations and the other solving the semiconductor equations. The presented methodology provides one with sufficient confidence in the adopted characterization techniques and results. Precisely, it allows one to differentiate between the accurate and erroneous characterizations. Further, the need for proper calibration and de-embedding techniques in high-frequency characterization is emphasized by investigating the s-parameters corresponding to a narrow-band amplifier at 170 GHz suitable for G-band radar applications.

On the other hand, intense research on the innovative design of BiCMOS compatible SiGe HBTs with increased speed and breakdown voltage is being pursued across the globe. In this direction of cutting-edge research, we present two unconventional SiGe HBT architectures with improved RF performance metrics. Our first design is based on a nanowire architecture that ensures reduced lateral parasitics leading to an fMAX above 900 GHz. The second architecture is an SOI-based lateral SiGe HBT that demonstrates an fMAX above 2.7 THz.