60nm collector InGaAs/InP Type-I DHBTs demonstrating 660 GHz fT, BVCEO = 2.5V, and BVCBO = 2.7V
We report InP/InGaAs/InP double heterojunction bipolar transistors (DHBT) fabricated using a conventional mesa structure. The devices employ a 14 nm highly doped InGaAs base and a 60 nm InP collector containing an InGaAs/InAlAs superlattice grade. Devices employing a 400 nm emitter exhibit a maximum fT = 660 GHz with a 218 GHz f max - this is a record fT for a DHBT. The devices have been scaled vertically for reduced base and collector electron transit times, and the base-collector mesa has been further scaled to minimize the capacitance Ccb associated with the base contact area. The peak current gain beta ap 95, BVCEO = 2.5 V, BV CBO = 2.7 V, and the devices operate in excess of 30 mW/mum 2