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

We report the performance of InP Double Heterojunction Bipolar Transistors (DHBT´s) with a chirped InGaAs/InP superlattice B-C junction grown by CBE. 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 highly doped thin layer was also included at the end of the CSL to offset the quasi-electric field arising from the grade and suppress further the carrier blocking effect across the B-C heterojunction. The InP/InGaAs CSL DHBT demonstrated a high BV/sub CEO/ of 18.3 V with a typical current gain of 55 with minimal carrier blocking up to high current densities. Maximum cutoff frequencies of f_max=146 GHz and f/sub r/=71 GHz were obtained from the fabricated 2×10 μm²-emitter DHBT.