Common Base Four-Finger InGaAs/InP Double Heterojunction Bipolar Transistor with Maximum Oscillation Frequency 535 GHz

A common base four-finger InGaAs/InP double heterojunction bipolar transistor with 535 GHz f_max by using the 0.5 μm emitter technology is fabricated. Multi-finger design is used to increase the input current. Common base configuration is compared with common emitter configuration, and shows a smaller K factor at high frequency span, indicating a larger breakpoint frequency of maximum stable gain/maximum available gain (MSG/MAG) and thus a higher gain near the cut-off frequency, which is useful in THz amplifier design.