InP/GaAsSb/InP double heterojunction bipolar transistors

InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) are some of the fastest bipolar transistors ever fabricated, with current gain cutoff and maximum oscillation frequencies simultaneously exceeding 300 GHz while maintaining breakdown voltages BV/sub CEO/ > 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 describe the implications of the staggered band line-up 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.