Photonic properties of ZnO epilayers

The characterization by various experimental techniques of homoepitaxial growth and photonic properties of ZnO epilayers was exhaustively analyzed. The photonic properties of ZnO as promising material for the realization of polariton lasers were investigated by angular dependent reflection spectroscopy. The fitting of the polariton dispersion curve with the experimental results provided us information about the longitudinal-transverse exciton-polariton splitting and damping constants. In addition, the valence band symmetry was examined by angular resolved magneto-optical photoluminescence. From our theoretical and experimental results we extracted evidence that the topmost A valence band possesses Г7 symmetry. Micro-Raman spectroscopy revealed even in homoepitaxially grown samples the existence of compressive or tensile strain which varied not only in the ZnO layers but also in the templates. In contrast, the untreated substrates were uniformly strained. Sporadically crystal perturbations culminating in the formation of separated growth domains were observed. Additionally, resonant Raman scattering was performed, showing a strong enhancement of the 2E1(LO) mode for resonant excitation of the I8 bound exciton complex. We suggest that the resonant Raman scattering led to a longer lifetime of the resonantly excited phonon mode due to a strong exciton-phonon interaction.

[1]  W. Y. Liang,et al.  Transmission Spectra of ZnO Single Crystals , 1968 .

[2]  P. H. Kasai,et al.  Electron Spin Resonance Studies of Donors and Acceptors in ZnO , 1963 .

[3]  M. Cardona.  Optical Properties of the Silver and Cuprous Halides , 1963 .

[4]  C. Thomsen,et al.  Resonant Raman scattering on free and bound excitons in GaN , 2001 .

[5]  R. Martin,et al.  Resonant Raman Scattering , 1983 .

[6]  J. Scott.  uv Resonant Raman Scattering in ZnO , 1970 .

[7]  A. Morita,et al.  Spin-Orbit Coupling in Ionic Crystals with Zincblende and Wurtzite Structures , 1965 .

[8]  D. C. Reynolds,et al.  Valence-Band Ordering in ZnO , 1999 .

[9]  H. Gong,et al.  Photoluminescence and multiphonon resonant Raman scattering in low-temperature grown ZnO nanostructures , 2006 .

[10]  R. Leite,et al.  Enhancement of Raman Cross Section in CdS due to Resonant Absorption , 1966 .

[11]  Alain Lusson,et al.  Strain-Fields Effects and Reversal of the Nature of the Fundamental Valence Band of ZnO Epilayers : Semiconductors , 2001 .

[12]  D. C. Reynolds,et al.  Exciton Spectrum of ZnO , 1966 .

[13]  R. Helbig,et al.  Band-edge emission in ZnO , 1976 .

[14]  J. Birman,et al.  Theory of Lattice Raman Scattering in Insulators , 1967 .

[15]  H. Nylén,et al.  Electronic structure of ZnO(0001) studied by angle-resolved photoelectron spectroscopy , 1997 .

[16]  D. C. Reynolds,et al.  Zeeman Effects in the Edge Emission and Absorption of ZnO , 1965 .

[17]  Karl Johnston,et al.  Identification of donor-related impurities in ZnO using photoluminescence and radiotracer techniques , 2006 .

[18]  Jürgen Christen,et al.  Bound exciton and donor–acceptor pair recombinations in ZnO , 2004 .

[19]  V. Ursaki,et al.  Multiphonon resonant Raman scattering in ZnO crystals and nanostructured layers , 2004 .

[20]  Manuel Cardona,et al.  Light Scattering in Solids VII , 1982 .

[21]  J. Shah,et al.  Bound Exciton Resonance in Raman Cross Sections in CdS , 1971 .

[22]  Patrick R. Briddon,et al.  Theory of Li in ZnO: A limitation for Li-based p -type doping , 2005 .

[23]  A. Kavokin,et al.  ZnO as a material mostly adapted for the realization of room-temperature polariton lasers , 2002 .

[24]  Andrew G. Glen,et al.  APPL , 2001 .

[25]  Manuel Cardona,et al.  Light Scattering in Solids , 2000 .

[26]  J. Gutowski,et al.  Forbidden luminescence and resonance Raman scattering of bound exciton states in CdS , 1983 .

[27]  D. G. Thomas.  The exciton spectrum of zinc oxide , 1960 .

[28]  B. Meyer,et al.  Valence-band ordering and magneto-optic exciton fine structure in ZnO , 2002 .

[29]  Suhuai Wei,et al.  Origin of p -type doping difficulty in ZnO: The impurity perspective , 2002 .

[30]  T. C. Damen,et al.  Antiresonance of Raman cross-sections for nonpolar phonons in CdS , 1971 .

[31]  Manuel Cardona,et al.  Resonant Raman scattering in ZnO , 1977 .

[32]  A. Uedono,et al.  Exciton–polariton spectra and limiting factors for the room-temperature photoluminescence efficiency in ZnO , 2005 .

[33]  V. Ursaki,et al.  Photoluminescence and resonant Raman scattering in highly conductive ZnO layers , 2004 .

[34]  Y. Liu,et al.  Resonant Raman scattering and photoluminescence from high-quality nanocrystalline ZnO thin films prepared by thermal oxidation of ZnS thin films , 2001 .

[35]  M. Strassburg,et al.  Magneto-optical properties of bound excitons in ZnO , 2003, cond-mat/0308315.

[36]  Michael Uhrmacher,et al.  Unambiguous identification of the PL-I9 line in zinc oxide , 2007 .

[37]  J. Sann,et al.  Group I elements in ZnO , 2005 .