在缩放的毫米波InP/GaInAsSb双异质结双极型晶体管中实现最优的碰撞电离限制击穿电压

Thin collector indium phosphide (InP)/gallium indium arsenide antimonide (GaInAsSb) double heterojunction bipolar transistors (DHBTs) exhibit higher open-base-collector–emitter (BVCEO) and open-emitter-collector–base breakdown (BVCBO) voltages than ternary InP/gallium arsenide antimonide (GaAsSb) DHBTs implemented with identical collector layers: with a GaInAsSb base, BVCEO and BVCBO values are 20% and 43% higher, respectively. The improvement mechanism has not yet been investigated. We show that InP/GaInAsSb DHBTs achieve impact ionization-limited open-base breakdown voltages BVCEO, i.e., the maximum theoretical (and therefore optimal) value for a given InP collector. To date, no other scaled InP DHBTs reach impact ionization limited BVCEO values: GaInAsSb bases thus unlock the full benefits of the high breakdown fields of pure InP collectors. The improved breakdown voltages with GaInAsSb follow from the reduction of interband tunneling between the base valence band and the InP collector conduction band with respect to a GaAsSb base. Measurements on GaAsSb- and GaInAsSb-based devices confirm that only GaInAsSb devices achieve impact ionization limited BVCEO values. The 43% measured improvement in BVCBO with a GaInAsSb base relative to a GaAsSb base is in good quantitative agreement with calculations based on interband tunneling theory. The ability to improve breakdown voltages in “Type-II” DHBTs without modifying the collector design (i.e., doping, thickness, or composition) is unique in bipolar transistors: it helps device designers to maximize transistor output power and power-added efficiency without degrading their cutoff frequencies f_ T / f_ MAX . For GaInAsSb bases, higher RF output power levels enabled by enhanced breakdown voltages are demonstrated in large-signal measurements at 94 GHz.