Output power of a double tunneling-injection quantum dot laser

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We develop a comprehensive theoretical model for a double tunneling-injection(DTI) quantum dot (QD) laser. Both electrons and holes are injected into QDsby tunneling from two separate quantum wells (QWs). Ideally, out-tunneling ofeach type of carriers from QDs into the opposite-to-injection-side QW should becompletely blocked; as a result, the parasitic electron–hole recombination outsideQDs will be suppressed and the light–current characteristic (LCC) of a laser willbe strictly linear. To scrutinize the potential of a DTI QD laser for high-poweroperation and the robustness of an actual device, our model includes out-tunnelingleakage of carriers from QDs. We complement our calculations by an analyticalmodel and derive closed-form expressions for the LCC and carrier populationacross the layered structure. We show that, even in the presence of out-tunnelingleakage, the flux of parasitic recombination outside QDs remains restricted withincreasing injection current. As a consequence, the LCC exhibits a remarkablefeature distinguishing the DTI QD laser from other types of injection lasers—itbecomes increasingly linear and the slope efficiency grows closer to unity at highinjection currents. The linearity is due to the fact that the current paths connectingthe opposite sides of the structure lie entirely within the QDs—in view of thethree-dimensional confinement in QDs, the out-tunneling fluxes of carriers from dots arelimited.