The effect of interdiffusion on the change of refractive index of an AlGaAs/GaAs quantum well structure

Abstract

The change of the refractive index due to quantum well (QW) disordering is calculated for light propagating normal to the Al_0.3Ga_0.7As/GaAs QW layers (i.e. along the QW growth direction). A hyperbolic function is used to model the above QW confinement profile after disordering, i.e. thermal interdiffusion of trivalent atoms across the well-barrier interfaces. The refractive index difference (Δn) is evaluated for two cases, where case I refers to the difference between a partially disordered QW and a more extensively disordered QW, while case II refers to the difference between an as-grown QW and a partially disordered QW. The results demonstrate that good photon confinement (large Δn > 0) can be achieved for both cases, where Δn increases with increasing QW width and decreases with annealing time for case I while for case II it increases with annealing time. In comparing the two cases, a shorter annealing time is required to achieve the same value of Δn if the case II structures are used. The change of refractive index obtained here demonstrates a larger value of Δn than that produced by the variation of the concentration of free carriers in the bulk material.