Carrier and photon dynamics in transversally asymmetric high-speed AlGaAs/InP MQW lasers

Abstract

Carrier transport and carrier capture were reported to markedly influence the carrier and photon dynamics in quantum-well semiconductor lasers and to limit the modulation bandwidth. Recently, model calculations of various degrees of complexity have isolated special aspects of the problem. We give an extended overview and report on our theoretical and experimental results on l.S5m AlGaInAs/InP lasers with strongly asymmetric transversal waveguide structures. The selfconsistent solution of the Poisson and continuity equations is based on measured carrier mobilities and not only limited to the confinement region. The confinement factor is pointed out to be important when comparing different asymmetric structures. The use of optimized asymmetric structures is demonstrated theoretically and experimentally to enable a distinct improvement in modulation bandwidth and to counteract the limiting physical processes such as carrier transport and carrier capture-escape. Finally, the influence of the shape of the longitudinal carrier and photon density profiles on the modulation behavior is studied. We found that a better homogenization of these profiles for transversally optimized structures may slightly increase the bandwidth. This is further confirmed experimentally by comparing lasers of different profiles applying chirped DFB gratings implemented by bent waveguides.