High current density and high power density operation of ultra high speed InP DHBTs

We report thermal design and characterization of high-current-density InP double heterojunction bipolar transistors (DHBT) designed for 150 GHz logic operation. Low thermal resistance DHBTs were obtained through the use of InP collectors and composite InGaAs/InP subcollectors containing as little as 12.5 nm InGaAs for ohmic contacts. When biased at J_e = 8 mA/μm² and V_ce = 1.45 V (11.6 mW/μm² dissipation), producing 370 GHz f_τ and 459 GHz f_max, the devices exhibit only 69°C emitter junction heating. The DHBTs operate without destruction at 10 mA/μm² at V_ce= 2 V, a 20 mW/μm² dissipation. We also report on the improvements obtained through reducing the InGaAs subcollector ohmic contact layer thickness for improved device heat-sinking into the substrate.