Contactless electroreflectance and photoluminescence characterization of Zn0.68Be0.06Mg0.26Se crystalline alloys

In this report, results of optical characterization of Bridgman-grown Zn0.68Be0.06Mg0.26Se crystalline alloys in the near-band-edge interband transitions region using temperature-dependent contactless electroreflectance (CER) and photoluminescence (PL) in the temperature range 10-300 K and time-resolved PL measurements at 10 K are presented. Two features with separation energy of 40 meV are observed in the near-band-edge CER spectra. The origins of these two features are attributed to the fundamental band-edge excitonic transitions of the coexisted different crystal phases in accordance with the X-ray diffraction and transmission electron microscope results. The increase of the broadening parameter of the excitonic feature of the PL spectra with increasing temperature has been attributed to the electron-longitudinal optical phonon interactions. In addition, the transient PL spectrum at 10 K in the excitonic emission region exhibits the asymmetric lineshape and can be deconvoluted into two Gaussian features with one order of magnitude difference in the decay time. These two components are assigned to the recombination of free excitons and localized excitons in this quaternary compound. (C) 2009 Elsevier B.V. All rights reserved.