Multifinger InP HBT's in Transferred-Substrate technology for 100 GHz power amplifiers

This paper reports results on a transferred-substrate InP heterojunction bipolar-transistor technology for high-frequency power stages. The basic building block is a 2-finger transistor with f_T and f_max values of 376 GHz and 385 GHz, respectively, at an emitter size of 0.8 × 5 μm². The transistors demonstrate more than 7 dB of gain at 96 GHz with good power densities of better than 3.7 mW/μm². For a 4-finger transistor, f_T and f_max reduce to 302/325 GHz while doubling the power. W-band amplifiers based on a single 2-finger transistor have reached a saturated output power of 14.8 dBm at 77 GHz with more than 10 dB return loss on input and output. The results confirm that the transistors are suitable for compact circuit design with minimum inter-stage matching.