Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session X41: Semiconductors: Electronic and Optical Properties |
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Sponsoring Units: FIAP Chair: Angelo Mascarenhas, National Renewable Energy Laboratory Room: Colorado Convention Center 504 |
Friday, March 9, 2007 8:00AM - 8:12AM |
X41.00001: Wire-like characteristics induced by vertically electronic coupling in stacked InAs/GaAs quantum dots superlattices Tzung-Te Chen , Yang-Fang Chen, Jyh Shyang Wang, Ying-Sheng Huang , Ru Shang Hsiao, Jenn Fang Chen, Chih Ming Lai, Jim Young Chi The wire-like characteristics of stacked InAs/GaAs quantum dots induced by vertically electronic coupling were demonstrated by surface photovoltaic and photoluminescence measurements. It is found that the surface photovoltaic signal can be enhanced by up to one hundred times due to the wire-like behavior along the growth direction. The emission from the cleaved edge surface is strongly anisotropic, which can be turned from the in-plane to normal to the plane polarization by changing the spacer thickness. Additionally, the electroluminescence of stacked quantum dots near 1.3 um based on the wire-like characteristics has a much better performance than that of uncoupled quantum dots. [Preview Abstract] |
Friday, March 9, 2007 8:12AM - 8:24AM |
X41.00002: Giant Spin-Orbit Bowing in GaAs$_{1-x}$Bi$_{x}$ A. Mascarenhas, B. Fluegel, S. Francoeur, S. Tixier, E. C. Young, T. Tiedje We report a giant bowing of the spin-orbit splitting energy $\Delta _{0}$ in the dilute GaAs$_{1-x}$Bi$_{x}$ alloy for Bi concentrations ranging from 0 to 1.8 {\%}. This is the first observation of a large relativistic correction to the host electronic band structure induced by just a few percent of isoelectronic doping in a semiconductor material. It opens up the possibility of tailoring the spin-orbit splitting in semiconductors for spintronic applications. [Preview Abstract] |
Friday, March 9, 2007 8:24AM - 8:36AM |
X41.00003: Valence Band Anticrossing in GaBi$_{x}$As$_{1-x}$ Kirstin Alberi, O.D. Dubon, W. Walukiewicz, K.M. Yu, K. Bertulis, A. Krotkus Recently, significant attention has been devoted to exploring the large bandgap bowing and spin-orbit splitting in GaBi$_{x}$As$_{1-x}$. alloys. We attribute the origins of these effects to a restructuring of the alloy valence band induced by an anticrossing interaction between the delocalized GaAs $p$-like states and the resonant localized Bi $p$-like states. Hybridization of like-symmetry states leads to the splitting of the heavy hole, light hole and spin-orbit split-off bands into sets of $E_{+}$ and $E_{-}$ subbands. The splitting is confirmed experimentally by photomodulated reflectance spectroscopy in alloys with Bi concentrations up to $x$ = 0.084. The bandgap bowing is a direct consequence of the strong upward shift of the uppermost heavy and light hole $E_{+}$ bands with increasing Bi concentration, while the much slower ascent of the spin-orbit split-off $E_{+}$ band produces the large rise in the spin-orbit splitting energy. [Preview Abstract] |
Friday, March 9, 2007 8:36AM - 8:48AM |
X41.00004: Interactions of Ga$_n$As$_{n}$ Clusters with CGaAs Cages: Possible Nanostructures Ajit Hira, Matilda Fernandez Extending our work on fullerene-alkali complexes$^{1}$, we now examine the interactions of small Ga$_{n}$As$_{n}$ clusters (n = 1 thru 10) with mixed CGaAs cage clusters. First, we derive the physical and chemical properties of the GaAs clusters, including their binding energies, bondlengths, ionization potentials and charge distributions. The geometries of the small gallium arsenide clusters are based on full optimizations. Electron correlation effects are included for binding energies and optimal intermolecular bondlengths. Next we focus on the physical and chemical properties of 60-atom mixed CGaAs cages. The optimization of the cages is subject to symmetry constraints. The third phase of the investigation examines the interactions of the small GaAs clusters with the CGaAs cages. For these complexes various properties, including dissociation channels and dissociation energies, are tabulated. We also explore the implications of this research for the design of nanostructures. 1. Daniel Bulnes, Nichole Moya-Leyba, Erica Velarde and Ajit Hira, " Theoretical Study of Na$_{3}$C$_{60}$ and Na$_{4}$C$_{60 }$Clusters: Pathways to Nanoscale Contacts", \textit{Bull. Am. Phys. Soc}. 50, 1475 (March 2005\textbf{).} [Preview Abstract] |
Friday, March 9, 2007 8:48AM - 9:00AM |
X41.00005: Persistent Currents in Higher Genus Materials and Structures David Schmeltzer, Avadh Saxena Persistent charge and spin currents have been usually studied in an isolated ring. However, recent semiclassical calculations and an experiment performed on sixteen connected GaAS/GaAlAs rings provide motivation to study persistent currents in higher genus structures. To this end, we introduce Dirac's second class constraint to explore high genus materials and ring structures. As a specific example we apply this method to compute the persistent charge current in a system of coupled rings. [Preview Abstract] |
Friday, March 9, 2007 9:00AM - 9:12AM |
X41.00006: Optical Transport Imaging for the Measurement of Electric Field and Minority Carrier Diffusion Length N.M. Haegel, P. Andrikopoulos, T.J. Mills An optical imaging technique is used to determine electric field and minority carrier diffusion length in planar heterostructures. We combine an optical microscope inside an SEM and image the spatial distribution of luminescence due to diffusion and drift from point source excitation. By comparing peak luminescence intensity with and without applied field, a quantitative measure of electric field value is obtained, while the transport image illustrates the field direction. Drift behavior has been imaged in a dimensionally confined region in a p type AlGaAs/GaAs double heterostructure where electron motion transitions from quasi 1D to 2D. Comparison to finite element modeling confirms the approach and demonstrates the sensitivity of the technique to local material and field variations. The technique can also be used for a 2 point measure of contact resistance. In the absence of applied field, the luminescence distribution provides a measure of minority carrier diffusion length, in a contact-free manner from a single image. This is demonstrated for a range of minority carrier diffusion lengths from $\sim $ 1.5 to 60 $\mu $m in III-V materials. The technique provides direct access to minority carrier mobility for studies of anisotropy, field dependence and domain behavior. We acknowledge support from NSF DMR-0203397 and DMR-0526330. [Preview Abstract] |
Friday, March 9, 2007 9:12AM - 9:24AM |
X41.00007: Electrical measurement of quantum interference population control in (111) GaAs Jared Wahlstrand, Ryan Smith, Jessica Pipis, Peter Roos, Steven Cundiff Two-color quantum interference control is the interference between absorption pathways, such as one- and two-photon absorption. Depending on the symmetry of the crystal, it can result in a ballistic current being injected or modulation of the carrier population. Previously, population control has been measured using an all-optical technique. We present results of an experiment in which we measured the carrier population modulation electrically using a Au/Ge electrode structure patterned on (111) GaAs. This is a more practical technique for potential applications, such as carrier-envelope phase detection.\footnote{T. M. Fortier, P. A. Roos, D. J. Jones, S. T. Cundiff, R. D. R. Bhat and J. E. Sipe, Phys. Rev. Lett. 92, 147403 (2004)} [Preview Abstract] |
Friday, March 9, 2007 9:24AM - 9:36AM |
X41.00008: Exciton binding energy and electron effective-mass in strain compensated InGaAsN/GaAs single Quantum Well Lifang Xu, Dinesh Patel, Carmen Menoni, Jengya Yeh, Luke Mawst, Nelson Tansu A detailed lineshape analysis of the temperature dependent photoluminescence spectra of In$_{0.4}$Ga$_{0.6}$As$_{1-y}$N$_{y}$/GaAs quantum well (QW) (y=0; 0.005) is carried out. The analysis extracts the binding energy of the e$_{1}$-hh$_{1}$ ground-state exciton which equals 9.72$\pm $1.24 meV and 17.5$\pm $0.9 meV for InGaAs and InGaAsN (N=0.5{\%}) single QW sample, respectively. By using a fractional dimension exciton binding energy model, an electron effective mass of m$_{e}$*=(0.11$\pm $0.015)m$_{0 }$ is determined for the highly strained dilute nitride single QW. [Preview Abstract] |
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