We report the observation of strong exciton-photon coupling in a ZnSe based microcavity fabricated using epitaxial liftoff. Molecular beam epitaxial grown ZnSe/Zn0.9Cd0.1Se quantum wells with a one wavelength optical length at the exciton emission were transferred to a SiO2/Ta2O5 mirror with a reflectance of 96% to form finesse matched microcavities. Analysis of our angle resolved transmission spectra reveals key features of the strong coupling regime: anticrossing with a normal mode splitting of 23.6meV at 20K; composite evolution of the lower and upper polaritons; and narrowing of the lower polariton linewidth near resonance. The heavy hole exciton oscillator strength per quantum well is also deduced to be 1.78 × 10 13 cm −2 .

We have determined the direct and exchange electron -electron and electron -hole Coulomb energies in CdSe/ZnSe quantum dots. The experiments are based on single dot photoluminescence at low temperature. By controlling the charging with a vertical transistor structure and by applying a symmetry-breaking magnetic field, we show how we can determine all the Coulomb energies. The direct Coulomb energies are responsible for large, ~20 meV, red-shifts of the emission on charging. The exchange Coulomb energies lead to a very pronounced fine structure splitting, up to 2.6 meV, for the neutral exciton.The physics of self-assembled quantum dots is dominated by quantization. The largest energy gap in the system is clearly the fundamental energy gap. The strong confinement potentials induced by the quantum dot lead to quantized energy levels for both electrons and holes with typical quantization energies of tens of meV. However, additional energy scales play an important role in the photonics of self-assembled quantum dots. Electrons and holes interact through the Coulomb interaction. The typical Coulomb energies are particularly large in CdSe/ZnSe quantum dots on account of the small dot size, relatively large effective masses and relatively small relative permittivity. Exchange energies are also important. While the electron-electron exchange plays a role only for exciton complexes containing two or more electrons, the electron-hole exchange plays a crucial role in determining the energies and spins of the neutral exciton. A hierarchy of energy scales therefore exists, from ~eV for the fundamental band gap to sub-meV for some components of the electron-hole exchange interaction. It is clearly a challenge to determine all these energies experimentally.Spectroscopy of quantum dot ensembles is of limited use in this quest as inhomogeneous broadening obscures all but the coarsest energies in the system. Spectroscopy of single dots removes the inhomogeneous broadening and, particularly at low temperature where the homogeneous broadening can be as small as a few µeV [1], in principle allows access to a complete spectroscopic picture. We report here spectroscopy on single CdSe/ZnSe quantum dots in a variety of experimental configurations. We control the charge through the realization of a vertical field effect transistor to determine the direct electronelectron and electron-hole Coulomb energies. We determine the electron-hole exchange energies from detailed spectroscopy of the neutral excitons in a symmetry-breaking magnetic field. As we show, this enables us to determine all the important energies in this system.The samples for these experiments were grown by molecular beam epitaxy. After n + -GaAs substrate preparation, we grow a ZnSe buffer at 390 °C. CdSe quantum dots are grown at the same temperature using 8 cycles in atomic layer epitaxy. The growth is then completed with 50 nm ZnSe overgrowth. The quantum dots emit at 2.38 eV at low temperature with an ensemble width of 52 meV. The quantum dot

Independent dynamic acousto-mechanical and electrostatic control of individual quantum dots in a LiNbO 3 -GaAs hybrid

MgS/ZnSe/GaAs multilayers with the MgS thickness ranging from 20 to 140 nm were grown at 300 °C by molecular beam epitaxy on [001] GaAs substrates. The samples were studied by using several X-ray methods and transmission electron microscopy. The coexistence of metastable zinc-blende (ZB) and rock-salt (RS) MgS structural phases were evidenced and discussed. The analysis of reciprocal space maps of the x-ray intensity distribution around asymmetrical reciprocal lattice nodes allowed us to determine the strain status of the MgS layers and to show that the ZB-MgS phase were pseudomorphic in also the case of the thickest film. The lattice parameter of the pure ΖΒ-MgS phase ranging between 0.56333< a MgS <0.56367 nm was obtained by extrapolation from X-ray diffraction data and

ZnO films were deposited on c‐Al2O3 using pulsed laser deposition both with and without N2 in the growth ambient. X‐ray diffraction revealed poorer crystal quality and surface morphology for one‐step growths with N2 in the ambient. A marked improvement in both the crystallographic and surface quality was obtained through use of two‐step growths employing nominally undoped ZnO buffer layers prior to growth with N2 in the ambient. All films showed majority n‐type conduction in Hall measurements. Post‐annealing for 30 minutes at 600 ºC in O2 systematically reduced both the carrier concentration and the conductivity. A base room temperature carrier concentration of ∼ 1016 cm–3 was linked to Al diffusing from the substrate. 4.2 K photoluminescence spectra exhibited blue bands associated with the growths having N2 in the ambient. Temperature dependent Hall measurements were consistent with N being incorporated in the films. Processed devices did not, however, show rectifying behaviour or electroluminescence. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)