Investigation of AlGaAs/GaAs superlattice-emitter resonant tunneling bipolar transistor (SE-RTBT)

A bipolar transistor with an i-Al_0.5Ga_0.5As/n⁺-GaAs superlattice emitter as both hole reflection barriers and electron tunneling barriers has been fabricated successfully. The AlGaAs/GaAs potential spike is eliminated by moving the heterointerface away from the emitter-base junction. Both the turn-on voltage of emitter-base and base-collector junctions are almost identical for the same current level. The room-temperature common-emitter current gain is over 60, and a collector-emitter offset voltage of 55 mV has been obtained with a base-to-emitter doping ratio of 10. Multiple differential negative resistance phenomena and different transistor operating regimes have been observed due to the tunneling effects in the AlGaAs/GaAs superlattice at 77 K. Calculated results are in agreement with experimental ones. Because of the existence of high peak-to-valley current ratios as well as current gain over 65, the SE-RTBT is suitable for multivalued logic circuit applications with relatively reduced complexity