Low turn-on voltage GaAs heterojunction bipolar transistors with a pseudomorphic GaAsSb base

We have developed GaAs heterojunction bipolar transistors (HBTs) with low turn-on voltage by using pseudomorphic GaAsSb as the base layer. The turn-on voltage of GaAs/GaAs0.91Sb0.09 HBT is 0.10 V lower than that of InGaP/GaAs HBT. The lower turn-on voltage is attributed to the smaller band gap of the GaAsSb base layer, indicating that GaAsSb is useful material for reducing turn-on voltage of GaAs HBTs. The current gain of 20 is obtained for GaAs/GaAs0.91Sb0.09 HBT, which is larger than those of previously reported GaAs/GaAsSb HBTs owing to the pseudomorphic, fully strained GaAsSb with no misfit dislocations. The knee voltage of 0.47 V is attained at the collector current density of 5×104 A/cm2. These results indicate that GaAs/GaAsSb HBTs have a great potential for reducing operating voltage and power dissipation.