A new functional, resonant-tunneling bipolar transistor with a superlattice emitter

We report a new resonant-tunneling bipolar transistor (RBT), in which electrons are injected from emitter to base by resonant-tunneling through the minibands in the i-AlGaAs/n⁺-GaAs superlattice emitter. The main feature of the device is the significant double negative-differential-resistance both at room temperature and low temperature. Two high peak-to-valley (PV) current ratios of 4:1 and 2.6:1 were obtained at 77 K. In the common emitter configuration, bistable output currents exist as controlled by the base-emitter voltage at critical values of V_BE = 2.5 V and V_BE = 3 V, respectively. In addition, two negative transconductance operation regions were obtained when the base-emitter voltage was applied. Yet, three different transistor action regions occur as the control base current is being applied. For base currents that are not high enough to bring the base-emitter junction to flat-band condition, common-emitter current gain up to 65 was obtained. This is the highest value ever reported in an RBT device using GaAs based materials. As control base current increases sufficiently to cause the base-emitter voltage drop beyond the flat-band condition, two different transistor action regions with smaller current gains of 38 and 35 are found. Furthermore, the first peak current is nearly equal to the second peak current and much larger than the second valley current. Thus the proposed device is attractive for multiple-valued logic circuits and frequency multipliers.