NONEQUILIBRIUM ELECTRON-TRANSPORT IN HETEROSTRUCTURE BIPOLAR-TRANSISTORS PROBED BY MAGNETIC-FIELD

We show that the static current-voltage characteristics of a heterojunction bipolar transistor are dramatically influenced by application of a magnetic field. Nonequilibrium base transport has a strong influence on collector/emitter breakdown voltage, VCEB. With a magnetic field applied perpendicular to the direction of the injected emitter current VCEB increases from 2.6 V at 0 T to 8 V at 8 T. In the same device with a magnetic field applied parallel to the current flow, the current gain increases by a factor of 2 over the same magnetic field range. Transistors which exploit nonequilibrium base and collector transport have qualitatively different behavior compared to conventional devices which use diffusive and drift-diffusive transport.