Common base four-finger InGaAs/InP DHBT with 535 GHz fmax

A common base four-finger InGaAs/InP DHBT with 535 GHz fmax using 0.5μm emitter technology is fabricated. Multi-finger design was used to increase input current. Common base configuration was compared with common emitter configuration, and demonstrated a smaller K factor at high frequency span, indicating a larger MSG/MAG breakpoint frequency and thus a higher gain when frequency reaches MAG region of common emitter devices.