EFFECTS OF HIGH-EXCITATION ON LOCALIZED EXCITONS IN CUBIC ZNCDS LATTICE-MATCHED TO GAAS

Effects of high excitation on localized excitons have been studied in cubic Zn0.42Cd0.58S lattice-matched to GaAs. The time-integrated photo luminescence (PL) spectrum at 2 K under weak excitation conditions (0. 025 mu J/cm(2)) was composed of a single emission peaking at 2.863 eV and its LO-phonon replica, The linewidth of the main peak was 18.5 meV . With increasing excitation energy density (I-ex), the spectra broade ned, especially on the lower energy side and a small shoulder appeared at about 2.85 eV for I-ex greater than or similar to 2 mu J/cm(2). In order to study the detailed mechanism, the nonlinear luminescence com ponent was studied by the population mixing technique. The positive si gnals were detected on the lower energy side (2.85 eV) at an I-ex valu e in the range between 1.8 and 2.9 mu J/cm(2). This nonlinear componen t was attributed to localized excitonic molecules.