Tunneling at emitter periphery in silicon nitride passivated InP/InGaAs HBTs

This work presents a new explanation of the abnormal injection phenomena at emitter-base junction of the silicon nitride passivated InP-based heterojunction bipolar transistors. We have suggested that the emitter mesa sidewall is accumulated and that thermionic field emission from this zone becomes the principal component of the collector current. The proposed theoretical model is in good agreement with experimental collector current Gummel plots and with atomic force microscopy measurements of mesa emitter edge.