Krämer, T: High-Speed InP Heterojunction Bipolar Transistors

This work examines design and performance issues of InP/
InGaAs/InP double heterojunction bipolar transistors (DHBT).
A transferred substrate (TS) technology has been developed
to optimize high frequency performance. The 3" wafer-level
process provides lithographic access to both the front- and
backside of DHBT epitaxy aligned to each other. The resulting
linear device set-up eliminates dominant transistor parasitics
and relaxes design trade-offs. The optimized device topology
manifests in excellent device performance. Transistors
of 0.8 × 5 µm2 emitter area feature fT = 420 GHz and fmax =
450 GHz at breakdown voltages BVCEO > 4.5 V. The more
than six-fold increase in current density to 18 mA/µm2 overcomes
the limitation of previously reported TS HBTs and is an
important contribution to outstanding high frequency and
power performance of the devices. Transistors of 0.8 × 5 µm2
emitter area combine very high frequency performance with
saturated output power Pout > 13.5 dBm at 77 GHz and DC
power handling over 100 mW. These are record values for
transistors with fT and fmax over 400 GHz.
Finally, TS processing has been developed to a fully millimeter
wave monolithic integrated circuit (MIMIC) compatible
technology. Traveling-wave amplifiers (TWA) demonstrate a
broadband gain G = 12.8 dB within 3-dB cutoff frequency up
to fc = 70 GHz.