A new S-shaped switch based on an InGaP/GaAs/InGaAs step-compositional-emitter heterojunction bipolar transistor

A functional InGaP/GaAs/InGaAs step-compositional-emitter heterojunction bipolar transistor (HBT) is fabricated and demonstrated. Due to the avalanche multiplication and discontinuous confinement effects for electrons at InGaP/GaAs heterojunction and InGaAs quantum well, an interesting triple-route S-shaped negative-differential-resistance switch is observed under inverted operation mode at room temperature. In addition, the excellent transistor performances including a high current gain of 220 and a low offset voltage of 60 mV are achieved under normal operation mode. Consequently, the excellent switching characteristic and transistor action of the studied HBT provides a promise for amplifier and multiple-valued logic circuit applications.