Frequency Limits of Bipolar Integrated Circuits

InP HBTs at the 500 nm scaling generation have attained 450 GHz balanced cutoff frequencies and ~4 V breakdown. With such devices, 150 GHz digital circuits (static dividers) have been demonstrated. 175 GHz amplifiers have been demonstrated with slower HBTs. We discuss transistor scaling laws and scaling limits for realizing digital and analog/RF circuits at sub-mm-wave frequencies; the most critical limitations are metal/semiconductor contact resistivities and dissipated power densities. Given present contact performance and thermal design, 230 GHz digital ICs and 300 GHz power amplifiers are feasible today.