Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session T32: Semiconducting Devices & Applications |
Hide Abstracts |
Sponsoring Units: FIAP Chair: Linda Olafsen, Baylor University Room: C144 |
Wednesday, March 23, 2011 2:30PM - 2:42PM |
T32.00001: Tunable nonadiabatic excitation in a single-electron quantum dot J.D. Fletcher, Masaya Kataoka, P. See, S.P. Giblin, T.J.B.M. Janssen, J.P. Griffiths, G.A.C. Jones, I. Farrer, D.A. Ritchie We report observation of nonadiabatic excitation of single electrons in a quantum dot. We have developed a way of measuring the excitation spectrum of the quantum dot formed in a tunable-barrier single-electron pump. When the confinement potential is deformed at sub-nanosecond timescales, electrons are excited to states with higher back-tunneling rates leading to a measureable reduction in the pumped current. In the presence of a perpendicular magnetic field we have observed that these states follow a Fock-Darwin spectrum. Our experiments demonstrate a simple model system to study nonadiabatic processes of quantum particles. [Preview Abstract] |
Wednesday, March 23, 2011 2:42PM - 2:54PM |
T32.00002: The dynamic quantum dot as an accurate electron pump Stephen Giblin, Samuel Wright, Jonathan D. Fletcher, Masaya Kataoka, Michael Pepper, J.T. Janssen, David Ritchie, Christine Nicoll, Dave Anderson, Geb Jones We have developed an accurate single electron pump based on a dynamic quantum dot realised in a GaAs two-dimensional electron system. We report an accurate comparison between the pump current and a reference current derived from quantum standards of voltage and resistance: the Josephson effect and quantum Hall effect. We find that, at a clock frequency of several hundred Megahertz, the pump can transfer one electron per clock cycle with an accuracy approaching 10 parts per million. We discuss the significance of this result in relation to the proposed re- definition of the SI base unit Ampere. Theoretical estimations of the pump error rate indicate that an accuracy of one part in a hundred million is attainable, making our type of pump a candidate for a metrological current standard. [Preview Abstract] |
Wednesday, March 23, 2011 2:54PM - 3:06PM |
T32.00003: Measurement of Tunneling Conductance of Two-Dimensional Electrons in a Si MOSFET Nanostructure Hong Pan, Matthew House, Ming Xiao, Hongwen Jiang The properties of strongly correlated two-dimensional electrons in semiconductor heterostructure continue to be of a fundamental interest of condensed matter physics [1]. A collection of transport studies have revealed a wealthy of interesting effects in the low-electron density limit, particularly in Si MOSFET structures [2]. In this talk, we present an alternative, tunneling conductance measurement of the 2D electrons in a Si MOSFET nanostructure. In our device, a global gate is used to control the 2D electron density. In addition, a set of small gates, as small as 50nm, forms a lateral tunneling barrier for the measurements. We find that there is a strong correlation between the still puzzling metal-insulator transition observed in transport [2] and our tunneling characteristics. The tunneling conductance is studied under different carrier density and in-plane Magnetic field. The project is supported by the NSF under Grant No. DMR-0804794. \\[4pt] [1] B. Spivak, S. V. Kravchenko, S. Kivelson, and X.P.A. Gao, Rev. Mod. Phys. 82, 1743 (2010). \newline [2] E. Abrahams, S. V. Kravchenko, M. P. Sarachik, Rev. Mod. Phys. 73, 251 (2001) [Preview Abstract] |
Wednesday, March 23, 2011 3:06PM - 3:18PM |
T32.00004: The magnetized quantum wire: a potential candidate to act as an {\em active} laser medium Manvir Kushwaha The fundamental issues associated with the magnetoplasmon excitations are investigated in a quantum wire characterized by a confining harmonic potential and subjected to a perpendicular magnetic field. We embark on the charge-density excitations in a two-subband model within the framework of Bohm-Pines' random-phase approximation. Essentially, the focus of our study is the intersubband (magnetoroton) collective excitation which changes the sign of its group velocity twice before merging with the respective single-particle continuum. The computation of the gain coefficient suggests an interesting and important application: the electronic device based on such magnetoroton modes can act as an {\it active} laser medium. The situation is analogous to the (quasi-two dimensional) superlattices where the crystal can exhibit a negative resistance: it can refrain from consuming energy like a resistor and instead feed energy into an oscillating circuit. [Preview Abstract] |
Wednesday, March 23, 2011 3:18PM - 3:30PM |
T32.00005: Gain-Induced Refractive Index Changes in Resonantly Pumped Optical Pumping Injection Cavity Lasers Linda Olafsen, Lauren Bain, Lauren Ice, Ben Ball An optical pumping injection cavity (OPIC) laser contains a type-II W active region enclosed between two GaSb/AlAsSb distributed Bragg reflector mirrors, where the thickness of the etalon cavity surrounded by the mirrors is tuned to the desired pump wavelength. Multiple reflections of the pump photons result in more efficient absorption of the pump beam and consequently higher efficiencies and lower lasing thresholds. An optical parametric oscillator is used to pump the OPIC lasers at resonance, where the threshold pump intensities are minimized and output efficiencies are maximized. The resonant pump wavelength is found to vary quadratically with temperature, not linearly as would be expected from temperature-dependence of the lattice constant and refractive indices. Possible sources of this nonlinearity are lattice heating and gain-induced changes in the refractive indices resulting from the increase of optical pumping intensity with temperature. Through spectral measurements using step-scan Fourier Transform Infrared spectroscopy and multilayer reflectivity modeling, the relative contributions of these possible sources of parabolic temperature dependence of resonant wavelength are investigated. [Preview Abstract] |
Wednesday, March 23, 2011 3:30PM - 3:42PM |
T32.00006: ABSTRACT WITHDRAWN |
Wednesday, March 23, 2011 3:42PM - 3:54PM |
T32.00007: Mapping of Strain and Induced Polarization in GaMnAs/GaAs nanowires Edwin Fohtung, A. Minkevich, A.A. Matyshev, M. Riotte, D. Grigoriev, T. Slobodskyy, V. Holy, O.G. Shpyrko, T. Baumbach The effects of surface energy and non-localized interactions are the two major physical mechanisms that guarantees size dependent of elastic properties at the nanoscale. With the limit for linear elasticity defined in the vicinity of the lattice parameter for most materials, non-localized interaction can only arise due to the discrete nature of matter and fluctuations in interatomic forces averaged out within the elastic tensors. Using an extended elasticity theory that introduces higher order perturbations to the classical energy density state of a crystalline material, we demonstrate the possibility of mapping the strain and polarization in device nanostructures with the aid of synchrotron radiation coherent diffraction imaging. We provide experimentally confirmed 2D mapping of the strain field and polarization in etched GaMnAs on GaAs periodic wires. [Preview Abstract] |
Wednesday, March 23, 2011 3:54PM - 4:06PM |
T32.00008: Reflectance Spectra of Plasmon Waveguide Interband Cascade Lasers Robert Hinkey, Zhaobing Tian, Rui Yang, Tetsuya Mishima, Michael Santos Non-invasive reflectivity measurements have been explored as a method for measuring the carrier concentrations of the Si-doped cladding layers of Plasmon-Waveguide Interband Cascade (IC) Lasers. We present measurements and modeling done both on the IC laser structures, as well as highly doped InAs films grown on GaAs substrates that were used to calibrate the Molecular Beam Epitaxy growth. We have found that there is a sharp drop in the signal of the reflectance spectrum for p- polarized light oscillating near the plasma frequency, which falls in the mid-infrared for the cladding layers of the laser structure. This feature in the spectrum is caused by the interaction of the incident light with collective plasmon modes, and is distinct from the plasma edge feature seen in the reflectance spectrum of semi-infinite samples. A similar ``plasma absorption'' effect has been observed in thin metal films in the ultraviolet. The doping concentration and layer thicknesses of the structure were obtained by fitting a modeled curve to the measured spectrum. We were able to obtain measurements of the cladding layer doping concentrations (in a range from 10$^{18}$ to 10$^{19}$ cm$^{-3}$) with values that were in good agreement with those found using Hall effect measurements. We will discuss how these results can aid in improving the design of mid-infrared plasmon waveguide lasers. [Preview Abstract] |
Wednesday, March 23, 2011 4:06PM - 4:18PM |
T32.00009: ABSTRACT WITHDRAWN |
Wednesday, March 23, 2011 4:18PM - 4:30PM |
T32.00010: Electrical and Optical Characterization of $\alpha $-Silicon Thin Films Kiran Shrestha, Tanweer Mirza Beig, Pradeep Gali, Prathyusha Nukala, Chris Littler, Vincent Lopes, Usha Philipose, Nigel Shepherd, A. J. Syllaios We report on progress in the characterization of amorphous silicon thin-films utilized in infrared detectors. Specifically, we have observed changes in the Raman spectra, resistivity, and activation energy in protocrystalline Si films grown by PECVD as substrate temperature, dopant type and concentration, and hydrogen dilution of the reactants are varied. Both n- and p-type films exhibit four Raman spectral peaks [1]. The TO Raman peak becomes better defined and shifts towards the crystalline TO energy for increasing substrate temperature or H dilution, or for decreasing dopant concentration. Hall and resistivity measurements as a function of both magnetic field and temperature on the same material have been conducted to better understand the relationships between specific growth parameters and key electrical properties.\\[4pt] [1] A. J. Syllaios, et al, ``Raman Characterization of Protocrystalline Silicon Films'', MRS Symp. Proc.Vol.1153, A16-04, 2009. [Preview Abstract] |
Wednesday, March 23, 2011 4:30PM - 4:42PM |
T32.00011: Single-Crystalline Germanium Nanowire Heterostructure for High-Performance Transistors and Spintronics Jianshi Tang, Kang L. Wang, Chiu-Yen Wang, Lih-Juann Chen The formation of single-crystalline Ni$_{2}$Ge/Ge/Ni$_{2}$Ge nanowire heterostructure and its field effect characteristics by controlled reaction between a Ge nanowire and Ni contacts were studied. Transmission electron microscopy (TEM) studies reveal a wide temperature range to convert the Ge nanowire to single-crystalline Ni$_{2}$Ge by a thermal diffusion process. The \textit{in-situ} reaction examined by TEM shows atomically sharp interfaces for the Ni$_{2}$Ge/Ge/Ni$_{2}$Ge heterostructure with good epitaxial matches of Ge[-110]//Ni$_{2}$Ge[0-11] and Ge(111)//Ni$_{2}$Ge(100). Field effect transistors (FETs) built on this nanowire heterostructure show a high-performance $p$-type FET behavior with an on/off ratio over 10$^{5}$ and a field-effect hole mobility of 210 cm$^{2}$/Vs. This nanowire heterostructure with atomically sharp interfaces opens an opportunity to achieve high-performance nanowire transistors and explore promising application in spintronics. [Preview Abstract] |
Wednesday, March 23, 2011 4:42PM - 4:54PM |
T32.00012: Schottky Barrier Heights in low-k dielectric/Cu Interconnects as Determined by X-ray Photoelectron Spectroscopy Marc French, Milt Jaehnig, Markus Kuhn, Benjamin French, Sean King In order to understand the various possible leakage mechanisms in low-k/Cu interconnects, a knowledge of the basic band alignment between Cu and low-k dielectric materials is needed but has gone largely unreported. In this regard, we have utilized X-ray Photoelectron Spectroscopy (XPS) to measure the Schottky Barrier at interfaces of importance to Cu/low-k interconnects. Specifically, we have utilized XPS to determine the Schottky Barrier at the interface between Cu and low-k SiCN capping layers deposited on Cu via Plasma Enhanced Chemical Vapor Deposition (PECVD). We have also utilized XPS to determine the Schottky Barrier at interfaces between Ta barrier layer materials and low-k SiOC:H ILD materials and the valence band alignment at low-k SiCN:H/SiOC:H interfaces. Lastly, the impact of various plasma surface treatments on the band alignment at these interfaces was also investigated. The cumulative results indicate that electron transport along the SiCN:H/SiOC:H may represent the lowest energy barrier path for line-line Schottky emission based leakage. [Preview Abstract] |
Wednesday, March 23, 2011 4:54PM - 5:06PM |
T32.00013: Plasma Process to Simultaneously Clean ILD and CMP Cu Surfaces Xin Liu, Sandeep Gill, Fu Tang, Sean King, R.J. Nemanich Low-k inter-layer dielectrics (ILD) with copper interconnects display advantages for reducing energy consumption in silicon technology. However, the processing induced degradation of the ILD low-k properties has become a challenge. In this work, we have employed remote N$_{2}$/H$_{2}$ plasma processes to simultaneously clean both low-k ILD (k=2.5) and chemical-mechanical polished (CMP) Cu surfaces. FTIR and C-V results indicate that N$_{2}$ plasma cleaning processes show low carbon abstraction as well as a relatively small increase in the dielectric constant (k=2.6). A carboxamide layer is formed which apparently inhibits further etching. In contrast, the k value increases to 3.5 after an H$_{2}$ plasma treatment. For the CMP-Cu surfaces, an N$_{2}$/H$_{2}$ plasma process at 380C effectively removes the oxide and carbon contamination. In addition, the affects of plasma-induced UV light has been studied, and the results indicate enhanced carbon depletion in the ILD. Degradation of the low-k properties is attributed to carbon abstraction which is enhanced by the plasma induced UV and hydrophilic character. The results establish a range of N$_{2}$/H$_{2}$ plasma processes for simultaneous cleaning of CMP Cu and low-k ILD surfaces. [Preview Abstract] |
Wednesday, March 23, 2011 5:06PM - 5:18PM |
T32.00014: Elastic properties of high porosity low-k thin films measured by Brillouin light scattering S. Bailey, R. Sooryakumar, S. King, G. Xu, E. Mays, C. Ege, J. Bielefeld The continued scale down of material components present increasing challenges to technology development in the semiconductor industry. In particular, with the introduction of more porous materials and air gaps to further reduce permittivity, one significant issue is that low-k dielectrics in interconnects have sufficient mechanical strength. Since nano-indentation methods are questionable at these ultra-small thicknesses there is a need for non-invasive methods to characterize the mechanical properties of such highly compact porous structures. In this talk results of Brillouin scattering to measure elastic constants of thin ($<$ 200 nm) low-k SiOC:H films with porosities up to 35{\%} will be presented. Discrete longitudinal and transverse acoustic standing modes and their transformation to propagating excitations are investigated. The resulting mode dispersions provide for the Poisson's ratio ($\nu$) and Young's modulus (E) and confirm that, for highest porosity, the reduction in dielectric constant does not result in severe degradation in $\nu$ and E. [Preview Abstract] |
Wednesday, March 23, 2011 5:18PM - 5:30PM |
T32.00015: Effective Materials Properties of Interconnections in Industrial Microprocessor Designs Mary Lanzerotti, Giovanni Fiorenza, Rick Rand This talk presents a methodology to evaluate tradeoffs between technology and design to obtain the highest performance in industrial VLSI designs [1]. It is well known that the most significant circuitry constraint is that signals must arrive on time. Since the design cycle is time-consuming and complex, there is a need to migrate designs to future technology nodes to amortize design cost. However, models do not exist [1] to guide designers in their evaluation of whether migrated designs will operate successfully in a future technology or whether migrated designs will cause chip failure. There is therefore a need to evaluate the impact of design changes on performance. This talk evaluates this impact and describes it as an effective change in material properties of the design interconnections. Model estimates are compared with industrial microprocessor design data [1]. References [1] M. Y. Lanzerotti, G. Fiorenza, R. Rand, ``Impact of interconnect length changes on effective materials properties (dielectric constant),'' \textit{Proc. Ninth International ACM Workshop on System-Level Interconnect Prediction (SLIP 2007)}, Austin, TX, USA, March 17-18, 2007. Online: http://www.informatik.uni-trier.de/$\sim$ley/db/conf/slip/slip2007.html, current as of 11-16-2010. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2025 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700