Band structures and optical properties of GaInAs quantum wires grown by strain-induced lateral ordering

Band structures and optical matrix elements of strained multiple quantum-wires (QWR's) are investigated theoretically via the effective bond-orbital model, which takes into account the effects of valence-band anisotropy and the band mixing. In particular, the Ga$_{1-x}$In$_x$As QWR's grown by strain-induced lateral ordering (SILO) are considered. Recently, long wavelength Ga$_{1-x}$In$_x$As QWR lasers have been fabricated via a single step molecular beam epitaxy technique which uses the SILO process.[1] Low threshold current and high optical anisotropy have been achieved. Multi-axial strains [combinations of biaxial strains in the (001) and (110) planes] for QWR's are considered, Our calculated anisotropy in optical matrix elements (for light polarized parallel versus perpendicular to the QWR's axis) is in good agreement with experiment. We also find that the strain tends to increase the quantum confinement and enhance the anisotropy of the optical transitions.Comment: 11 papges, 10 figure

Systematic study of Ga1−x_{1-x}Inx_xAs self-assembled quantum wires with different interfacial strain relaxation

A systematic theoretical study of the electronic and optical properties of Ga$_{1-x}$In$_x$As self-assembled quantum-wires (QWR's) made of short-period superlattices (SPS) with strain-induced lateral ordering is presented. The theory is based on the effective bond-orbital model (EBOM) combined with a valence-force field (VFF) model. Valence-band anisotropy, band mixing, and effects due to local strain distribution at the atomistic level are all taken into account. Several structure models with varying degrees of alloy mixing for lateral modulation are considered. A valence force field model is used to find the equilibrium atomic positions in the QWR structure by minimizing the lattice energy. The strain tensor at each atomic (In or Ga) site is then obtained and included in the calculation of electronic states and optical properties. It is found that different local arrangement of atoms leads to very different strain distribution, which in turn alters the optical properties. In particular, we found that in model structures with thick capping layer the electron and hole are confined in the Ga-rich region and the optical anisotropy can be reversed due to the variation of lateral alloying mixing, while for model structures with thin capping layer the electron and hole are confined in the In-rich region, and the optical anisotropy is much less sensitive to the lateral alloy mixing.Comment: 23 pages, and 8 figure

Table of Contents

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Table of Contents

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Optics and Quantum Electronics

Contains table of contents on Section 3 and reports on nineteen research projects.Defense Advanced Research Projects Agency Grant F49620-96-0126Joint Services Electronics Program Grant DAAH04-95-1-0038National Science Foundation Grant ECS 94-23737U.S. Air Force - Office of Scientific Research Contract F49620-95-1-0221U.S. Navy - Office of Naval Research Grant N00014-95-1-0715Defense Advanced Research Projects Agency/National Center for Integrated Photonics TechnologyMultidisciplinary Research InitiativeU.S. Air Force - Office of Scientific ResearchNational Science Foundation/MRSECU.S. Navy - Office of Naval Research (MFEL) Contract N00014-91-J-1956National Institutes of Health Grant R01-EY11289U.S. Navy - Office of Naval Research (MFEL) Contract N00014-94-0717Defense Advanced Research Projects Agency Contract N66001-96-C-863

DEVLOPMENT OF NOVEL FUNCTIONAL

Rare-earth doped thin films are drawing increasing attention for their use in amplifiers and lasers and their suitability for integrated optics. The optical properties of rareearth ions in solids have been investigated widely and are well understood. Er3+-doped materials are attracting much attention because of the search for solid-state-laser devices operating in the green region, optical devices for 3D displays and for waveguides, which can work in telecommunication window. In this dissertation we researched and fabricated different novel functional thin films for photonics devices fabricated by RF-magnetron sputtering method as – Erbium-doped SiO2 Tantalum pentoxide [Ta2O5] Erbium-doped Tantalum pentoxide [Er-TaOx] Erbium- Ytterbium co-doped Tantalum pentoxide We fabricated different thin films using the RF-sputtering method and then annealed them at various temperatures and time durations. PL peaks were observed at wavelengths of 550 and 670 nm from the Er-TaOx films. We observed the strongest intensities of the 550 and 670 nm peaks from the samples with 0.96 and 0.63 mol% Er concentrations after annealing at 900° C for 20 min, respectively. To the best of our knowledge, this is the first report of light emission from Er-TaOx films fabricated by the RF-sputtering method. These results demonstrate that Er-TaOx films fabricated by RF sputtering can serve as high quality luminescent layers. These can easily be combined with other passive devices to realize novel active devices (e.g., a green-light-emitting photonic crystal), as only sputtering and annealing processes are needed for fabrication. Recent reports of optical waveguides fabricated on Ta2O5, higher nonlinear susceptibility χ3 of Ta2O5, and light emission from thin films makes Ta2O5 a promising material for novel photonic devices.学位記番号：工博甲39