Magneto-oscillations in the bipolar quantum-well resonant tunneling transistor

Magneto-oscillations due to a minority carrier two-dimensional electron gas (2DEG) in the base of a bipolar quantum-well resonant tunneling transistor at liquid helium temperatures are described. The 2DEG forms in a wide (20 nm) setback layer adjacent to an abrupt emitter/base heterojunction, often used in conventional HBTs as well as in the BiQuaRTT. The 2DEG has unusual capacitive effects at low temperature, since the sheet density increases to a maximum near 10/sup 12/ /cm/sup 2/ at flat-band conditions, then decreases at higher emitter/base bias. The high-mobility 2DEG accounts for the high lateral recombination, but may allow an effective reduction of base resistance, improving the high frequency response.