Disordering induced by impurity diffusion in ZnSe-based superlattices and optical waveguides fabricated by disordering

The phenomenon of layer disordering in CdZnSe/ZnSe and ZnSe/ZnS strained layer superlattices (SLSs) by Ge diffusion and the fabrication of ZnSe-based optical waveguides using the Ge-induced layer disordering in the superlattices has been studied. Both the as-grown sample and the sample annealed without a Ge layer showed several orders of well-resolved double crystal x-ray satellite peaks due to SLS periodic structure. However, the satellite peaks completely disappeared in the Ge-diffused sample, indicating that the SLS structure was disordered by the Ge diffusion and not caused by the annealing process. Photoluminescence (PL) measurements at 1.4 K of both the as-grown and the annealed samples without Ge diffusion show identical, sharp excitonic emission around 483 and 420 nm in CdZnSe/ZnSe SLS and ZnSe/ZnS SLS, respectively. After Ge diffusion, the PL peaks shift to higher energy, confirming the layer disordering of the SLS. The optically guided mode in the SLS guiding layer confined by the disordered alloy was confirmed, and a propagation loss α as low as 0.96 cm^-1 was obtained.