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In Al As – In P ∕ Ga As Sb ∕ In P double heterojunction bipolar transistors (HBTs) with InAlAs–InP composite emitter have been grown, fabricated, and characterized at various temperatures from 77to400K. The InAlAs–InP composite emitter structure effectively reduces electron pileup in the InP∕GaAsSb base-emitter junction and hence increases current gain, especially in the low-base-current region. The turn-on voltage shows a slightly different temperature dependence (−1.66mV∕K) from conventional InGaAs based HBTs due to the composite emitter. The activation energy study for the base (0.74eV) and collector currents (0.98eV) indicates the high quality of the base layer and the effect of InAlAs–InP composite emitter.

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InGaP/GaAs double heterojunction bipolar transistors (DHBTs) with composite collector has been proposed and fabricated to obtain the suitable heterojuncton bipolar transistor (HBT) for power amplifiers in wireless communication. The composite collector combines both wide-bandgap (InGaP) and narrow-bandgap (GaAs) materials. In the composite collector, InGaP material provides high breakdown field and thus is able to be employed to reduce thickness of collector while keeping the same breakdown voltage. GaAs materials provides higher electron mobility and thus is used to reduce on-resistance and transit time.In this work, a DHBT with composite collector (DHBT-C) is presented to demonstrate its improved power performance. 7803-8595-0/04/$20,00 0 2 0 0 4 IEEE. 0-