Type I InP/InGaAs/InP double heterojunction bipolar transistors were fabricated using a simple mesa structure, where emitter junction widths have been scaled from 250 nm to 200 nm. These devices exhibit f max in excess of 800 GHz, and f tau = 360 GHz. Greater than fifty percent device yield was obtained by employing two 25 nm SiNx sidewalls to protect and anchor the refractory metal emitter contact to the emitter semiconductor. A hybrid dry and wet etch process is used to form a vertical emitter mesa, causing reductions in both the emitter-base gap resistance Rgap and the spreading resistance beneath the emitter Rb,spread, leading to an expected and observed increase in f max. Peak HBT current gains beta ap 21-33, BVceo ~ 4 V, BVcbo ~ 5 V, and Je at low Vcb is over 10 mA/mum2.
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