Static and Dynamic Characteristics of In(AsSb)/ GaAs Submonolayer Lasers

The gain spectrum and modulation characteristics of ridge-waveguide laser diodes with InAs/GaAs submonolayer (SML) stacks have been investigated in detail. A comparison between active regions with intentionally altered inhomogeneous broadening is presented. The inhomogeneous broadening is controlled via Sb incorporation into the SML allowing for broader gain bandwidth and 3-D confinement of holes. In that way, the degree of charge-carrier localization can be tuned at a given wavelength. A slight performance loss at a given operation wavelength is observed due to a smaller optical overlap for the intentionally broadened gain medium. Still, bit rates up to 17 GBit/s can be obtained with the prospect for wider wavelength tunability. Multiple stacks of Sb-containing SMLs are suggested to enhance the optical overlap, which eventually allows for widely tunable quantum-dot lasers with larger modulation bandwidth.