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To overcome the limitations placed on the operating characteristics of diode lasers by recombination outside their active region, two novel designs were proposed for them: one using double tunneling-injection (injection of both electrons and holes) into the active region, and the other using two asymmetric barrier layers (ABLs) flanking the active region. The barrier layers are asymmetric in that they have considerably different heights for the carriers of opposite signs. The ABL located on the electron- (hole-) injecting side of the structure provides a low barrier (ideally no barrier) for electrons (holes) [so that it does not prevent electrons (holes) from easily approaching the active region] and a high barrier for holes (electrons) [so that holes (electrons) injected from the opposite side of the structure do not overcome it]. The use of ABLs should thus ideally prevent the simultaneous existence of electrons and holes (and hence parasitic electron-hole recombination) outside the active region. In this work, we calculate the threshold and power characteristics of quantum dot lasers with ABLs. We show that quantum dot lasers with ABLs offer close-to-ideal performance: low threshold current density, very high characteristic temperature (virtually temperature-independent operation), close-to-unity internal differential quantum efficiency, and linear light-current characteristic. |
