Optical properties of excitons in ZnO-based quantum well heterostructures

Recently the developments in the field of II?VI-oxides have been spectacular. Various epitaxial methods have been used to grow epitaxial ZnO layers. Not only epilayers but also sufficiently good-quality multiple quantum wells (MQWs) have been grown by laser molecular-beam epitaxy (laser-MBE). We mainly discuss the experimental aspect of the optical properties of excitons in ZnO-based MQW heterostructures. Systematic temperature-dependent studies of optical absorption and photoluminescence in these MQWs were used to evaluate the well-width dependence and the composition dependence of the major excitonic properties. Based on these data, the localization of excitons, the influence of exciton?phonon interaction and quantum-confined Stark effects are discussed. The optical spectra of dense excitonic systems are shown to be determined mainly by the interaction process between excitons and biexcitons. The high-density excitonic effects play a role in the observation of room-temperature stimulated emission in the ZnO MQWs. The binding energies of exciton and biexciton are enhanced from the bulk values, as a result of quantum-confinement effects.

[1]  H. Ohta,et al.  Thin-Film Transistor Fabricated in Single-Crystalline Transparent Oxide Semiconductor , 2003, Science.

[2]  H. Koinuma,et al.  Size dependence of exciton–longitudinal-optical-phonon coupling inZnO/Mg0.27Zn0.73Oquantum wells , 2002 .

[3]  Bernard Gil,et al.  Oscillator strengths of A, B, and C excitons in ZnO films , 2001 .

[4]  H. Koinuma,et al.  Room-temperature luminescence of excitons in ZnO/(Mg, Zn)O multiple quantum wells on lattice-matched substrates , 2000 .

[5]  Luo,et al.  Femtosecond coherent spectroscopy of bulk ZnSe and ZnCdSe/ZnSe quantum wells. , 1994, Physical review letters.

[6]  Zikang Tang,et al.  Room-temperature stimulated emission of excitons in ZnO/(Mg, Zn)O superlattices , 2000 .

[7]  H. Koinuma,et al.  Optical spectra in ZnO thin films on lattice-matched substrates grown with laser-MBE method , 2000 .

[8]  S. Sugano,et al.  Interband Optical Transitions in Extremely Anisotropic Semiconductors. I. Bound and Unbound Exciton Absorption , 1966 .

[9]  David Vanderbilt,et al.  Polarization-based calculation of the dielectric tensor of polar crystals , 1997 .

[10]  J. Hopfield.  a Quantum-Mechanical Theory of the Contribution of Excitons to the Complex Dielectric Constant of Crystals. , 1958 .

[11]  Masashi Kawasaki,et al.  High Mobility Thin Film Transistors with Transparent ZnO Channels , 2003 .

[12]  J. Hvam.  Exciton-exciton interaction and laser emission in high-purity ZnO , 1973 .

[13]  A. Terekhov,et al.  The influence of phonons and impurities on the broadening of excitonic spectra in gallium arsenide , 1976 .

[14]  Y. Segawa,et al.  Plasma-assisted molecular beam epitaxy for ZnO based II–VI semiconductor oxides and their heterostructures , 2000 .

[15]  H. Büttner,et al.  Effective Hamiltonians and bindings energies of Wannier excitons in polar semiconductors , 1977 .

[16]  Rudin,et al.  Temperature-dependent exciton linewidths in semiconductors. , 1990, Physical review. B, Condensed matter.

[17]  N. Fujimura,et al.  Formation of two-dimensional electron gas and the magnetotransport behavior of ZnMnO/ZnO heterostructure , 2003 .

[18]  Michael S. Shur,et al.  The influence of the strain‐induced electric field on the charge distribution in GaN‐AlN‐GaN structure , 1993 .

[19]  Colocci,et al.  Well-width and aluminum-concentration dependence of the exciton binding energies in GaAs/AlxGa1-xAs quantum wells. , 1993, Physical review. B, Condensed matter.

[20]  R. Langer,et al.  Giant electric fields in unstrained GaN single quantum wells , 1999 .

[21]  Masashi Kawasaki,et al.  Optically pumped stimulated emission in ZnO/ZnMgO multiple quantum wells prepared by combinatorial techniques , 2001, SPIE OPTO.

[22]  H. Koinuma,et al.  Temperature dependence of excitonic absorption spectra in ZnO/Zn0.88Mg0.12O multiquantum wells grown on lattice-matched substrates , 2001 .

[23]  R. L. Weiher,et al.  Contribution of Excitons to the Edge Luminescence in Zinc Oxide , 1968 .

[24]  H. Koinuma,et al.  STRUCTURE AND OPTICAL PROPERTIES OF ZNO/MG0.2ZN0.8O SUPERLATTICES , 1999 .

[25]  Masashi Kawasaki,et al.  Combinatorial Laser Molecular Beam Epitaxy (MBE) Growth of Mg–Zn–O Alloy for Band Gap Engineering , 1999 .

[26]  A. Many,et al.  Surface Quantum Wells in Hydrogen Implanted ZnO , 1999 .

[27]  K. Bajaj,et al.  Excitonic transitions in ZnO/MgZnO quantum well heterostructures , 2001 .

[28]  J. Zucker,et al.  Room temperature excitonic absorption in CdZnTe/ZnTe quantum wells: Contributions to exciton linewidth , 1991 .

[29]  Benjamin J. Norris,et al.  ZnO-based transparent thin-film transistors , 2003 .

[30]  O. Ambacher,et al.  Characterization of InGaN thin films using high-resolution x-ray diffraction , 2000 .

[31]  S. Oktyabrsky,et al.  Defects and interfaces in epitaxial ZnO/α-Al2O3 and AlN/ZnO/α-Al2O3 heterostructures , 1998 .

[32]  H. Koinuma,et al.  Thermal stability of supersaturated MgxZn1−xO alloy films and MgxZn1−xO/ZnO heterointerfaces , 1999 .

[33]  Syassen,et al.  Effect of pressure on the low-temperature exciton absorption in GaAs. , 1990, Physical review. B, Condensed matter.

[34]  Satoshi Masuda,et al.  Transparent thin film transistors using ZnO as an active channel layer and their electrical properties , 2003 .

[35]  H. Koinuma,et al.  Exciton spectra of ZnO epitaxial layers on lattice-matched substrates grown with laser-molecular-beam epitaxy , 2000 .

[36]  Pierre Lefebvre,et al.  Influence of electron-phonon interaction on the optical properties of III nitride semiconductors , 2001 .

[37]  F. Salvan,et al.  Radiative Recombination in Highly Excited CdS , 1969 .

[38]  H. Koinuma,et al.  Biexciton emission from ZnO/Zn0.74Mg0.26O multiquantum wells , 2001 .

[39]  Michael G. Spencer,et al.  Heteroepitaxy of ZnO on GaN and its implications for fabrication of hybrid optoelectronic devices , 1998 .

[40]  G. Mahan,et al.  Phonon-Broadened Impurity Spectra. I. Density of States , 1965 .

[41]  E. Weber,et al.  Elastic moduli of gallium nitride , 1997 .

[42]  Maan,et al.  Magnetoluminescence of the two-dimensional electron-hole fluid. , 1991, Physical review. B, Condensed matter.

[43]  S. Choopun,et al.  Observation of resonant tunneling action in ZnO/Zn0.8Mg0.2O devices , 2002 .

[44]  T. Chikyow,et al.  Heteroepitaxial growth of β-LiGaO2 thin films on ZnO , 2002 .

[45]  H. Koinuma,et al.  Well-width dependence of radiative and nonradiative recombination times in ZnO/Mg0.12Zn0.88O multiple quantum wells , 2001 .

[46]  R. McLean,et al.  Transparent ZnO thin-film transistor fabricated by rf magnetron sputtering , 2003 .

[47]  Shun Lien Chuang,et al.  Comparison of zinc-blende and wurtzite GaN semiconductors with spontaneous polarization and piezoelectric field effects , 2000 .

[48]  S. Permogorov,et al.  Free exciton motion in crystals and exciton-phonon interaction , 1966 .

[49]  Akira Ohtomo,et al.  Band gap engineering based on MgxZn1−xO and CdyZn1−yO ternary alloy films , 2001 .

[50]  Roberto Cingolani,et al.  Chapter 5 Optical Properties of Excitons in ZnSe-based Quantum Well Heterostructures , 1997 .

[51]  Luo,et al.  Quasi-two-dimensional excitons in (Zn,Cd)Se/ZnSe quantum wells: Reduced exciton-LO-phonon coupling due to confinement effects. , 1992, Physical review. B, Condensed matter.

[52]  C. Gourdon,et al.  Exciton Transfer between Localized States in CdS1–xSex Alloys , 1989 .

[53]  T. Yao,et al.  Layer-by-layer growth of ZnO epilayer on Al2O3(0001) by using a MgO buffer layer , 2000 .

[54]  H. Koinuma,et al.  Radiative recombination of electron–hole pairs spatially separated due to quantum-confined Stark and Franz–Keldish effects in ZnO/Mg0.27Zn0.73O quantum wells , 2002 .

[55]  H. Koinuma,et al.  Enhancement of exciton binding energies in ZnO/ZnMgO multiquantum wells , 2002 .

[56]  Masashi Kawasaki,et al.  Growth of ZnO Thin Film by Laser MBE: Lasing of Exciton at Room Temperature , 1997 .

[57]  G. Mahan,et al.  Phonon-Assisted Recombination of Free Excitons in Compound Semiconductors , 1968 .

[58]  E. Fridell,et al.  Microreactor for studies of low surface area model catalysts made by electron-beam lithography , 2000 .

[59]  J. Massies,et al.  Large size dependence of exciton-longitudinal-optical-phonon coupling in nitride-based quantum wells and quantum boxes , 2002 .

[60]  Akira Ohtomo,et al.  Stimulated emission induced by exciton–exciton scattering in ZnO/ZnMgO multiquantum wells up to room temperature , 2000 .

[61]  Pierre Lefebvre,et al.  Quantum confined Stark effect due to built-in internal polarization fields in (Al,Ga)N/GaN quantum wells. , 1998 .