Collector characteristics and the differential optical gain of a quantum-well transistor laser

The collector electrical characteristics $(I-V)$ of a transistor laser (TL) manifest directly the transport and recombination dynamics of the vital quantum-well (QW) base region, including as described here QW recombination state changes. By employing the continuity equations and an extension of the classic charge control model, we extract from the dc $I-V$ characteristics the differential optical gain of a single QW TL showing the QW state changes. The results agree in form with calculations employing Fermi’s golden rule and the “staircaselike” density of states of a QW.