Quantum-well intermixing influence on GaInNAs/GaAs quantum-well laser gain: theoretical study

The effect of quantum-well intermixing on the material gain of a GaInNAs/GaAs quantum-well laser is investigated theoretically. The diffusion of gallium and indium atoms in the intermixed sample is assumed and their compositional profiles are modelled using Fick's law. The band-anti-crossing model is used to calculate the band structure of the GaInNAs quantum well, which is appropriate for this non-randomly-alloyed material system. The calculated results show good agreement with the observed photoluminescence excitation for both non-intermixed and intermixed samples, which confirms this model. It is found that the strain gradient, the variation of material band gap and the degeneracy between heavy and light holes are the main factors determining the quantized energy levels of the intermixed quantum well. With the increase of diffusion length, the material gain and differential gain decrease due to the increase of the conduction band effective mass and the rapid decrease of the dipole moments. These characteristics of quantum-well intermixing effects will be useful in the design of integrated photonic devices based on this material.