NONLINEAR-OPTICAL PROPERTIES AND BLUE-LIGHT-EMITTING DIODE OF ZNSE/ZNS AND ZNTE/ZNS STRAINED-LAYER SUPERLATTICES

This paper reviews recent work on the nonlinear optics of ZnSe/ZnS and ZnTe/ZnS strained-layer superlattices (SLSs), with emphasis on their use in novel devices. The transmission spectra of ZnSe/ZnS SLS grown on CaF2 reveal the importance of excitonic processes, showing large energy shifts due to quantum confinement and strain. Refractive index modification and layer disordering of such superlattices results from implantation of N+ and Li+ ions. A transverse electric field spatially separates charge carriers. This leads to changes in the photoluminescence and optical transmission of ZnSe/ZnS SLS. Optical switching devices and optical frequency doublers are demonstrated. By analysing the excitation power dependence of PL from ZnTe/ZnS doping superlattices, it is confirmed that the dominant emission process involves recombination across the indirect gap in real space between conduction band electrons and impurity band holes. Blue-light-emitting diodes at room temperature were fabricated using p-ZnTe/ZnS doping SIS. It is clear that the optical properties of the ZnSe/ZnS and ZnTe/ZnS SLS are very useful for novel opto-electronic devices in the visible spectral region.