200-nm InGaAs/InP type I DHBT employing a dual-sidewall emitter process demonstrating ƒmax ≫ 800 GHz and ƒτ = 360 GHz
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 ƒ<inf>max</inf> in excess of 800 GHz, and ƒ<inf>τ</inf> = 360 GHz. Greater than fifty percent device yield was obtained by employing two 25 nm SiN<inf>x</inf> 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 R<inf>gap</inf> and the spreading resistance beneath the emitter R<inf>b,spread</inf>, leading to an expected and observed increase in ƒ<inf>max</inf>. Peak HBT current gains β ≈ 21–33, BV<inf>ceo</inf> ∼ 4 V, BV<inf>cbo</inf> ∼ 5 V, and J<inf>e</inf> at low V<inf>cb</inf> is over 10 mA/μm<sup>2</sup>.