Integrated fabrication of InGaP/GaAs δ-doped heterojunction bipolar transistor and doped-channel field effect transistor

Novel InGaP/GaAs co-integrated structures consisting of a heterojunction bipolar transistor and a field effect transistor are fabricated and demonstrated. For the HBT, the confinement effect for holes is increased and the potential spike at emitter-base (E-B) heterojunction is reduced significantly owing to the presence of a δ-doped sheet at the InGaP/GaAs junction. High current gain and low offset voltage are achieved. On the other hand, for a FET, an undoped InGaP gate layer is used to increase gate breakdown voltage, and a thin and heavy-doped GaAs channel is shown to enhance current drivability, transconductance, and linearity. For this structure, a wide gate voltage range larger than 3 V with the transconductance larger 150 mS/mm is obtained.