A Double-Heterojunction Bipolar Transistor Having a Degenerately Doped Emitter and Backward-Diode Base Contact

A double-heterojunction bipolar transistor having a degenerately doped emitter layer is investigated. The base-emitter Esaki diode introduces very low input impedance in the off- state but does not degrade the current gain at high forward bias. The heavily doped emitter layer makes it possible to scale the emitter-layer thickness considerably. The heavily doped emitter layer also allows contacting the base via the base-emitter backward diode. The high-frequency performance of the device is presented.