InGaAs/InP DHBTs in a Dry-Etched Refractory Metal Emitter Process Demonstrating Simultaneous $f_{\tau}/f_{\max} \sim \hbox{430/800}\ \hbox{GHz}$
Abstract-We report an InPZIn<sub>0.53</sub>Ga<sub>0.47</sub>As/InP double heterojunction bipolar transistor (DHBT) demonstrating simultaneous 430-GHz f<sub>τ</sub> and 800-GHz f<sub>max</sub>. The devices were fabricated using a triple mesa process with dry-etched refractory metals for emitter contact formation. The devices incorporate a 30-nm-thick InP emitter semiconductor which enables a wet-etch emitter process demonstrating 270-nm-wide emitter-base junctions. At peak RF performance, the device is operating at 30 mW/μm<sup>2</sup> with J<sub>c</sub> = 18.4 mA/μm<sup>2</sup> and V<sub>ce</sub> = 1.64 V. The devices show a peak DC common-emitter current gain (β) ~ 20 and V<sub>BR,CEO</sub> = 2.5 V.