InGaAs-InP mesa DHBTs with simultaneously high f(T) and f(max) and low C-cb/I-c ratio

We report an InP–InGaAs–InP double heterojunction bipolar transistor (DHBT), fabricated using a conventional triple mesa structure, exhibiting a 370–GHz and 459–GHz max, which is to our knowledge the highest reported for a mesa InP DHBT—as well as the highest simultaneous and max for any mesa HBT. The collector semiconductor was undercut to reduce the base–collector capacitance, producing a cb ratio of 0.28 ps/V at cb = 0 5 V. The BR CEO is 5.6 V and the devices fail thermally only at 18 mW m, allowing dc bias from = 4 8 mA m at ce = 3 9 V to = 12 5 mA m at ce = 1 5 V. The device employs a 30 nm carbon-doped InGaAs base with graded base doping, and an InGaAs–InAlAs superlattice grade in the base–collector junction that contributes to a total depleted collector thickness of 150 nm.