Characterization of InAlAs/In0.25Ga0.75As0.72Sb0.28/InGaAs double heterojunction bipolar transistors

We report on the characterization of InP-based heterojunction bipolar transistors (HBTs) with low turn-on voltage and high current gain by using InGaAsSb as the base layer. The low turn-on voltage of 0.43 V is attributed to the smaller band gap of the In_0.25Ga_0.75As₀₇₂Sb_0.28 material. High current gain of 74 is observed despite a heavily Be-doped (9.0×10¹⁹ cm^-3) base is used, suggesting a long minority carrier lifetime (τ_n) in the InGaAsSb material. Moreover, low specific contact resistivity of 5×10^-8 Ω-cm² is also demonstrated on separate In_0.25Ga_0.75As₀₇₂Sb_0.28 samples.