Excitons, biexcitons, and phonons in ultrathin CdSe/ZnSe quantum structures

2019-10-27 02:13:43

quantum ZnSe CdSe dependent biexcitons

责任者: Gindele, F.;Woggon, U.;Langbein, W.;Hvam, J.M.;Leonardi, K.;Hommel, D.;Selke, H. 单位: Inst. fur Exp. Phys., Dortmund Univ., Germany 来源出处: Physical Review B (Condensed Matter)(Phys. Rev. B, Condens. Matter (USA)),15 Sept. 1999,60(12):8773-82 摘要: The optical properties of CdSe nanostructures grown by migration-enhanced epitaxy of CdSe on ZnSe are studied by time-, energy-, and temperature-dependent photoluminescence and excitation spectroscopy, as well as by polarization-dependent four-wave mixing and two-photon absorption experiments. The nanostructures consist of a coherently strained Zn1-xCdxSe/ZnSe quantum well with embedded islands of higher Cd content with sizes of a few nanometer due to strain-induced CdSe accumulation. The local increase in CdSe concentration results in a strong localization of the excitonic wave function, in an increase in radiative lifetime, and a decrease of the dephasing rate. Local LO-phonon modes caused by the strong modulation of the Cd concentration profile are found in phonon-assisted relaxation processes. Confined biexcitons with large binding energies between 20 and 24 meV are observed, indicating the important role of biexcitons even at room temperature 关键词: biexcitons;binding energy;cadmium compounds;excitons;II-VI semiconductors;interface phonons;interface states;island structure;light absorption;multiwave mixing;nanostructured materials;photoluminescence;radiative lifetimes;semiconductor quantum dots;semiconductor quantum wells;time resolved spectra;zinc compounds;excitons;biexcitons;phonons;ultrathin CdSe/ZnSe quantum structures;optical properties;CdSe nanostructures;migration-enhanced epitaxy;time-dependent photoluminescence;energy-dependent photoluminescence;temperature-dependent photoluminescence;excitation spectroscopy;polarization-dependent four-wave mixing;two-photon absorption;nanostructures;coherently strained Zn1-xCdxSe/ZnSe quantum well;embedded islands;strain-induced CdSe accumulation;localization;excitonic wave function;radiative lifetime;dephasing rate;local LO-phonon modes;phonon-assisted relaxation processes;confined biexcitons;large binding energies;room temperature;20 C;CdSe-ZnSe