Linear and Nonlinear Optics of Wide-Gap II-VI Semiconductors

Abstract

The purpose of this contribution is to review some of the present activities in II–VI semiconductor research at this institute. In the field of bulk materials, the IR spectra of ZnO:Ga are presented with electron densities up to 2 × 1020 cm—3. The density dependence of the plasmon–phonon mixed states is given. In alloy semiconductors we investigate the temperature dependence of the absolute external luminescence yield, which reaches values close to unity for selected CdS1—xSex samples. Furthermore the incoherent population dynamics below and above laser threshold is measured, including the observation of self pulsation in the stimulated output. The investigation of the dynamics and of the excitation spectra of the luminescence of CdS and of ZnSe based quantum wells gives information about the relaxation process and the coupling to (barrier) LO phonon modes. The slow thermalization of hot free excitons in ZnSe QWs is observed directly in time-resolved luminescence in the phonon-sideband region. For CdSe quantum dots in a glass matrix, data of the exchange splitting and the coupling to quantized acoustic phonons are given as a function of the dot radius. CdS quantum dots with organic cladding layers and high volume fraction show between ITO and Ag contacts an electroluminescence which can be tuned by the applied voltage through the whole visible spectrum.