Lateral and vertical scaling of high-fmax InP-Based HBTs

Design approach to improving f(max) of 10-based HBTs by combining lateral scaling (lithographic scaling) and vertical scaling (improving f(T)) is discussed. An HBT scaling model is formulated to provide means of analyzing the essential impact of scaling on f(max). The model was compared with measurements of single and double heterojunction bipolar transistors with different f(T) and various emitter sizes. While a high f(max) of 313 GHz was achieved using submicron HBT with high f(T), it was found that further improvement could have been obtained by reducing the emitter resistance, which has imposed considerable limit on lateral scaling.