AlSb-InAs-AlSb p-n-p transistors with low turn-on voltage, narrow bases, and low base resistance

The authors built and characterized transistors with base widths from 100 nm to as thin as 25 nm. The transistors were grown on GaAs substrates and fabricated into emitter-up double-mesa structures. Driving equivalent current densities requires an emitter-base voltage more than 1 V below that needed in graded-junction GaAs HBTs (heterojunction bipolar transistors) or a half volt less than Si bipolars. These devices supplied finite current gain for emitter-base voltages above 300 mV. The gain was current-dependent, peaking at about beta =25 for the narrowest bases, and appeared to be limited by recombination at the emitter-base interface. The transistors supported a collector-to-emitter voltage of V/sub CE/>2.5 V. Intrinsic base resistances were extremely low.