Control of InP/InGaAs heterojunction bipolar transistor performance through the use of undoped collectors

Theoretical and experimental investigations using InP/InGaAs heterojunction bipolar transistors (HBTs) with and without undoped collectors are reported. A steady-state and transient Monte Carlo technique was used to evaluate each design. The switching and steady-state performance of the undoped collector HBT is faster (1.33 ps vs. 2.10 ps switching, and 1.35 ps vs. 2.64 steady-state performance) at a given collector current density. A self-aligned HBT process using reactive ion etching (RIE) for reaching the base is described. Conventional and undoped collector devices had h_fe gains on the order of 63 and maximum cutoff frequency of 18 GHz using a 2 μm×11μm emitter geometry