Light-emitting p⁺nn⁺-heterotransistors with nn-heterojunction base/collector

We consider a p⁺nn⁺-heterodiode with an additional nn-heterojunction in the n-base that plays a role of the base/collector junction. Such a device can be a very effective light-emitting phototransistor or transistor. A depletion layer of the added intermediate heterojunction splits the diode n-base into two new bases: wider-bandgap phototransistor (transistor) base 1 and narrower-bandgap light emitting base 2 that serves simultaneously as the collector region of the phototransistor (transistor). A coefficient of light-to-light conversion (of an input light absorbed in base 1 into an output light emitted from base 2) can be very high due to very high phototransistor gain. Effects of avalanche multiplication on the depletion layer of the intermediate heterojunction, edge multiplication in an accumulation layer of the same junction, and thermionic emission across a conduction band discontinuity barrier are taken into account. This discontinuity barrier can be high enough (>0.5-0.7 eV) for effective implementation of the suggested transistor, phototransistor and light-to-light converter. We discuss various material systems appropriate for implementation of these devices (namely InAs/GaSb/AlSb-system and InGaAs/InAlAs/InP-system). Criteria of stability of the described transistor regime are considered, and transition to a thyristor (light emitting photothyristor) regime is discussed.