InP/GaAsSb/InP double heterojunction bipolar transistors (invited)

InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) are some of the fastest bipolar transistors and maximum ever fabricated, with cut-rent gain cutoff oscillation frequencies simultaneously exceeding 300 GHz while maintaining breakdown voltages BVCEO > 6 V. InP/GaAsSb/InP DHBTs are particularly appealing because excellent device figures of merit are achievable with relatively simple structures involving abrupt junctions and uniform doping levels and compositions: this is a tremendous manufacturability advantage in comparison to GaInAs-based alternatives. This paper highlights some important physical aspects of the use of GaAsSb base layers. In particular, we will describe the implications of the staggered band lineup at the E/B and B/C heterojunctions for charge storage in the devices, and show that InP/GaAsSb/InP DHBTs offer inherent advantages with direct implications to applications in high-speed digital circuits.