InP double heterojunction bipolar transistors with chirped InGaAs/InP superlattice base-collector junction grown by CBE

InP DHBT´s with a chirped InGaAs/InP superlattice B-C junction, which were grown by CBE, have been fabricated and characterized. The B-C junction of the DHBT was graded with a 10-period InGaAs/InP chirped superlattice (CSL) between the InGaAs base and the lightly doped InP collector. A delta-doped thin layer was included at the end of the CSL to offset the quasielectric field arising from the grade and suppress further the carrier blocking effect across the B-C heterojunction. The InP/InGaAs CSL DHBT with a 6000 Å-thick InP collector demonstrated a high BV_CEO of 18.3 V and a BV_BCO of 22.8 V with a typical current gain of 55. Maximum cutoff frequencies of f_max =146 GHz and f_T=71 GHz were obtained from the fabricated single-finger 2×10 μm²-emitter DHBT. The devices with different emitter dimensions were also fabricated and characterized