Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session X35: Semiconducting Devices and Applications |
Hide Abstracts |
Sponsoring Units: FIAP Chair: Tom Oder, Youngstown State University Room: Morial Convention Center 227 |
Friday, March 14, 2008 8:00AM - 8:12AM |
X35.00001: Improved Ni/SiC and ZrB$_{2}$/SiC Schottky Barrier Diodes by High Temperature Processing Tom Oder, Ta-Lun Sung, Edward Sutphin, Sara Schaefer, Rani Kummari High temperature processing was used to improve the barrier properties of SiC Schottky diodes fabricated with Ni and ZrB$_{2}$ Schottky contacts. The Ni/SiC diodes were annealed in vacuum at 500 $^{\circ}$C in 20-hour intervals for a total of 110 hours. The average Schottky barrier heights determined by I-V measurements, increased with annealing time from 1.48 eV for non-annealed contacts to 1.81 eV for those annealed for 20 hours. The improvement is believed to be due to the formation of nickel silicide. The ZrB$_{2}$ Schottky contacts for the ZrB$_{2}$/SiC diodes were deposited at temperatures between 20 $^{\circ}$C and 800 $^{\circ}$C. The barrier heights increased with the deposition temperature from an average value of 0.87 eV for contacts deposited at 20 $^{\circ}$C to 1.07 eV for those deposited at 600 $^{\circ}$C. The Rutherford backscattering spectra of the ZrB$_{2}$/SiC contacts revealed a decrease of oxygen with increase in the deposition temperature and showed no reaction at the ZrB$_{2}$/SiC interface. We ascribe the improvement of the ZrB$_{2}$/SiC diodes to the removal of oxygen from the contact when deposited at high temperatures. [Preview Abstract] |
Friday, March 14, 2008 8:12AM - 8:24AM |
X35.00002: ``Ultimate'' SOI MOSFETs Thomas J. Walls, Konstantin K. Likharev Silicon-On-Insulator (SOI) field-effect transistors (MOSFETs) are being aggressively scaled toward the 10-nm frontier - see, e.g., Ref. \footnote{M. Vinet {\it et al., IEEE Elec. Dev. Lett.}, vol. 26, pp. 317-319, May 2005.}. In our earlier work \footnote{V. Sverdlov {\it et al., IEEE Trans. on Electron Dev.}, vol. 50, pp. 1926-1933, Sep. 2003.}, we have carried out a detailed analysis of the performance and parameter variation sensitivity of double-gate sub-10-nm MOSFETs using a self-consistent numerical solution of the 2D Poisson equation and 1D Schrodinger equation. However, for very small devices the 1D approximation misses some important details of the device physics. In this work, we have used the momentum-space formalism, developed in 1989 by A. Szafer and A. D. Stone \footnote{A. Szafer {\it et al., Phys. Rev. Lett.} vol. 62, pp. 300-303, Jan. 1989}, to fully account for 2D quantum effects. At the meeting, we will present a comparison of our new results with our previous 1D approximation, as well as calculations of the gate capacitance of the transistors. This work has been supported in part by the ONR. [Preview Abstract] |
Friday, March 14, 2008 8:24AM - 8:36AM |
X35.00003: Novel Ferroelectric CMOS Circuits as a Nonvolatile Logic M. Takahashi, T. Horiuchi, Q.-H. Li, S. Wang, K. Y. Yun, S. Sakai We propose a novel and promising nonvolatile-logic circuit constructed by p channel type (Pch) and n channel type (Nch) ferroelectric gate field effect transistors (FeFETs), which we named a ferroelectric CMOS (FeCMOS) circuit. The circuit works as both logic and memory. We fabricated a NOT logic FeCMOS device which have Pt metal gates and gate oxides of ferroelectric SrBi$_{2}$Ta$_{2}$O$_{9}$ (SBT) and high-$k$ HfAlO on Si. Key technology was adjusting threshold voltages of the FeFETs as well as preparing those of high quality. We demonstrate basic operations of the NOT-logic response, memory writing, holding and non-destructive reading. The memory writing is done by amplifying the input node voltage to a higher level when the node was logically high and to a lower one when it was logically low just before the writing operation. The data retention was also measured. The retained high and low voltages were almost unchanged for 1.2 days. The idea of this FeCMOS will enhance flexibility of circuit designing by merging logic and memory functions. This work was partially supported by NEDO. [Preview Abstract] |
Friday, March 14, 2008 8:36AM - 8:48AM |
X35.00004: Study on threshold voltages of Pt/SrBi$_{2}$Ta$_{2}$O$_{9}$/Hf-Al-O/Si FeFETs Q.-H. Li, M. Takahashi, S. Wang, T. Horiuchi, C.C. Wang, K.Y. Yun, Y. Fuhihata, S. Sakai Complementary ferroelectric-gate field-effect transistors (FeFETs) are attractive for nonvolatile-logic circuit applications after the achievement of long data retention for both $n$- and $p$- channel FeFETs [1, 2]. To demonstrate nonvolatile logic circuits, the threshold voltage should be well controlled. Due to ferroelectricity two threshold voltages $V_{t, left}$ and $V_{t, right}$ can be defined from $I_{d}-V_{g}$ curves as gate voltages at $I_{d}$ =10$^{-6}$A. More than 90 $n$- or $p$-channel Pt/SrBi$_{2}$Ta$_{2}$O$_{9}$/Hf-Al-O/Si FeFETs on a Si chip are studied. The average$ V_{t, left}$ and $V_{t, right}$ are 1.19 and 2.38 V for $n$-channel FeFETs, and -0.76 and 0.40 V for $p$-channel FeFETs, respectively. The standard deviations of $V_{t}$ are 3-5{\%} and 7-8{\%} of the memory window for the $n$- and $p$- channel FeFETs, respectively. $V_{t}$ positions are adjusted by varying the well doping concentrations. Our results indicate possible circuit demonstration. This work was partially supported by NEDO. \newline [1] S. Sakai, et al, \textit{IEEE Electron Devices Lett.}, \textbf{25}, 369(2004). \newline [2] Q.-H. Li, et al , \textit{Appl. Phys. Lett. }\textbf{89}, 222910 (2006). [Preview Abstract] |
Friday, March 14, 2008 8:48AM - 9:00AM |
X35.00005: The Nanowire iJFET Bart Soree, Wim Magnus The cylindrical geometry of nanowire surrounding gate MOSFETs gives rise to outstanding electrostatic control in comparison to planar devices. On the other hand, we expect that for ultrasmall nanowire diameters, the interaction of electrons with the surface (e.g. surface roughness and high-k) will be detrimental for device performance due to mobility degradation. In order to avoid these surface interactions we consider a surrounding gate nanowire operated not in MOSFET mode, but in ``JFET mode.'' We thus consider a nanowire with silicon body radius $R$ and surrounding oxide of thickness $t_{\rm ox}$ with a surrounding metal gate where both source, drain and silicon body are doped uniformly with a donor density $N_ {\rm D}$. Applying a negative gate voltage pushes the electrons away from the interface between the insulator and metal gate, and as a result a depletion region is induced. For sufficient negative gate voltage the depletion region reaches the center of the silicon body, and pinch-off occurs. For large radii, we construct a compact model, and we show that reasonable pinch- off voltages are realized when the wire radius or the donor density is sufficiently small. Using the gradual channel approximation we are able to obtain current-voltage characteristics that constitute a ``proof of concept'' for this device. In the case of ultrasmall radii, we perform a quantum mechanical analysis of the electronic structure. [Preview Abstract] |
Friday, March 14, 2008 9:00AM - 9:12AM |
X35.00006: Extraordinary Electroconductance in Ti-GaAs hybrid thin film structures Yun Wang, A.K.M. Newaz, Jian Wu, S.A. Solin, V.R. Kavasseri, Niu Jin, I.S. Ahmad, I. Adesida Following the demonstration of extraordinary electroconductance (EEC) in metal-semiconductor hybrids (MSHs), we have developed microscopic circular thin film GaAs-Ti EEC sensors capped by a concentric Ti electrode that acts as both a shunt and Schottky barrier. The geometrical properties of the device are characterized by the parameter $\alpha $ which is the ratio of the shunt radius to that of the GaAs mesa. We investigated samples with $0\le \alpha \le {14} \mathord{\left/ {\vphantom {{14} {16}}} \right. \kern-\nulldelimiterspace} {16}$ in mesa sizes from 80$\mu $m to 200$\mu $m. We define the EEC as the {\%} change of conductance with and without an externally applied electric field. An EEC=20{\%} is obtained with $\alpha $=8/16 at E=0.65kV/cm and a shunt bias current of 50nA. The reverse bias EEC is always larger than the forward bias effect (maximum $\sim $ 5{\%}) due to the asymmetry of the band profile. The {\%} change in sample conductance increases linearly with direct reverse voltage bias across the MS interface and is independent of the radius of the GaAs mesa. This independence is extremely desirable for scaling to the nano regime. Such a static electric field sensor as described above makes high resolution imaging of surface charge density distribution possible. [Preview Abstract] |
Friday, March 14, 2008 9:12AM - 9:24AM |
X35.00007: Optimizing Transport Properties of a Potential Molecular Electronic Device Julio L. Palma, Chao Cao, Hai-Ping Cheng, Jeffrey L. Krause Future generations of electronic devices will have the dimensions of molecular size. The ability to control the transport properties of single molecules will have a major impact on this promising technology. The azobenzene molecule has been proposed recently as a component of a light-driven molecular switch. This molecule has two stable conformations in its ground state: {\it cis} and {\it trans}. The molecule can be converted from one configuration to the other by photo-excitation. Previous calculations showed that the {\it trans} configuration has a considerably higher conductance than the {\it cis} configuration. In this work, we study the effects of chemical substituents on the electron transport properties of azobenzene. The effects of such substituents are crucial in predicting structures that may have optimized properties with slightly different chemical structures. For the azobenzene studies, we include electron donating groups (-NH$_2$) and electron withdrawing groups (-NO$_2$) in meta- and -ortho positions with respect the azo group. The transport properties are calculated using first principles methods that combine non-equilibrium Green's function (NEGF) technique with density functional theory (DFT). [Preview Abstract] |
Friday, March 14, 2008 9:24AM - 9:36AM |
X35.00008: Ion Sources for Deep and Shallow Ion Implantation Ady Hershcovitch, V. Batalin, A. Bugaev, V. Gushenets, B. Johnson, A. Kolomiets, G. Kropachev, R. Kuibeda, T. Kulevoy, I. Litovko, E. Masunov, E. Oks, V. Pershin, S. Petrenko, S. Polozov, H. Poole, I. Rudskoy, D. Seleznev, P. Storozhenko, A. Svarovski, G. Yushkov Various ions, but mostly B, P, Sb, {\&} As, are implanted, over a wide range of energies into materials used in the construction of semiconductors. These energies range from as low as 100 eV for shallow surface implantations, to as high as multi-MeV for deep implantation into the substrate. State of the art ion sources meet industry needs for the energy range of 10 keV to 300 keV. But at the two extremes (100's of eV and at multi-MeV), there is room for improvement due to space charge limitations at the low energy range and due to inefficiency in acceleration at the higher energy range. A joint R{\&}D effort focusing on meeting industry needs has been in progress for the past four years. This endeavor has resulted in record steady state output currents of higher charge state Antimony and Phosphorous ions as well as Decaborane molecular ions. This talk is a synopsis of an extensive ion source R{\&}D program designed to address industry needs. [Preview Abstract] |
Friday, March 14, 2008 9:36AM - 9:48AM |
X35.00009: Infrared Near-field Microscopy of Semiconductor Devices Fritz Keilmann, Andy J. Huber, Rainer Hillenbrand We report optical imaging at ultrahigh resolution $<$ 30 nm of cross-sectional preparations of state-of-the-art transistors. Our technique employs a scanning optical near-field microscope of scattering type (s-SNOM). It is based on a tapping-mode AFM with a standard, metallized tip, and an interferometric receiver. This detects a pseudo-heterodyne signal detection that is filtered at a low harmonic of the tapping frequency. The illumination wavelength of 10.7 $\mu $m allows to record specific contrasts---which are obtained in amplitude as well as in phase---distinguishing not only all material components in the transistors, but furthermore highlighting the charge carriers. Prospects of quantitative carrier density mapping will be discussed. A.J. Huber et al., Adv. Mat. 19, 2209 (2007) [Preview Abstract] |
Friday, March 14, 2008 9:48AM - 10:00AM |
X35.00010: Resistance Switching Behavior in Epitaxially Grown NiO S.R. Lee, J.H. Bak, Y.D. Park, K. Char, D.C. Kim, R. Jung, S. Seo, X.S. Li, G -S. Park, I.K. Yoo Reproducible resistance switching behavior has been found in NiO films prepared by a pulsed laser deposition system. The I-V measurements of epitaixally grown NiO on SrRuO$_{3}$ electrode show a bipolar resistive memory switching behavior, in contrast with a unipolar switching behavior of polycrystalline NiO on Pt electrode. In order to understand the resistive memory switching mechanism in NiO, the I-V characteristics and memory switching property of epitaxial NiO prepared under various synthesis conditions and electrodes has been investigated. The IV measurements at room temperature suggest that the interface between NiO and the electrode plays an important role on the resistive switching phenomena. To analyze the role of the interface, our efforts to control the interfaces and to measure the I-V characteristics at low temperature will be presented. [Preview Abstract] |
Friday, March 14, 2008 10:00AM - 10:12AM |
X35.00011: Temperature-Dependence of the Resonant Pump Wavelength in Optical Pumping Injection Cavity Lasers L.J. Olafsen, K.G. Young, T.C. McAlpine, W.W. Bewley, I. Vurgaftman, J.R. Meyer, H. Lee, R.U. Martinelli 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 varies linearly with temperature. In addition to presenting light-light results, including efficiencies and thresholds as a function of temperature, the temperature-dependence of the resonant pump wavelength will be discussed, including the relative variations and contributions of lattice constant and refractive index with temperature. [Preview Abstract] |
Friday, March 14, 2008 10:12AM - 10:24AM |
X35.00012: Mid-IR Photonic-Crystal Interband Cascade Lasers Mijin Kim, Chul Soo Kim, William Bewley, Chadwick Canedy, James Lindle, Jill Nolde, Diane Larrabee, Igor Vurgaftman, Jerry Meyer Photonic-crystal distributed-feedback (PCDFB) semiconductor lasers have the potential to maintain optical coherence over very large areas. We report an electrically pumped PCDFB laser operating in a true single mode in the mid-infrared. A two-dimensional grating was formed on top of an interband cascade laser emitting at 3.3 $\mu $m by patterning a high-index Ge layer. The grating and the 400-$\mu $m-wide gain stripe were tilted by 20$^{o}$ with respect to the facet. Current spreading was prevented by ion bombarding the region outside the gain stripe rather than etching of a ridge. The gain region at the back of the cavity was also terminated by ion bombardment, since feedback from the back facet is undesirable. A single mode was emitted with maximum cw output power $>$ 60 mW, resolution-limited spectral linewidth (side-mode suppression ratio 27 dB), and single-lobe spatial far-field with angular full width at half maximum of 0.5$^{o}$. Comparison of the near and far field patterns indicated effective $M^{2} \quad \approx $ 3. The observation of low efficiency is thought to be due primarily to inadequate grating coupling, which can be remedied by thickening the Ge layer. [Preview Abstract] |
Friday, March 14, 2008 10:24AM - 10:36AM |
X35.00013: ABSTRACT WITHDRAWN |
Friday, March 14, 2008 10:36AM - 10:48AM |
X35.00014: Electrical Characterization of Critical Phase Change Conditions in Nanoscale Ge$_{2}$Sb$_{2}$Te$_{5 }$ Pillars Ozhan Ozatay, Barry Stipe, Jordan Katine, Bruce Terris Following the original work of Ovshinsky on disordered semiconductors that exhibit ovonic threshold switching (OTS) there has been substantial interest in the electronic reversible switching properties of chalcogenides$^{1}$. The current induced phase transitions between polycrystalline and amorphous states in these materials offer orders of magnitude changes in the conductance which makes them an ideal candidate for non-volatile data storage applications. In this work we investigate the scaling of critical programming conditions required to observe such transitions between highly resistive (disordered) and highly conductive (ordered) states by constructing a resistance map with various pulse widths and amplitudes under different cooling conditions (as a function of pulse trailing edge). We study the evolution of critical phase change conditions as a function of contact size (50nm-1$\mu $m) and shape (circle-square-rectangle). We compare the resulting switching behaviour with the predictions of a finite-element model of the electro-thermal physics to analyze the nature of the switching dynamics at the nanoscale. $^{1}$ S-H. Lee, Y. Jung, R. Agarwal, \textit{Nature Nanotechnology}; doi:10:1038/nnano.2007.291 [Preview Abstract] |
Friday, March 14, 2008 10:48AM - 11:00AM |
X35.00015: Charge Transport Phenomena in Detectors of the Cryogenic Dark Matter Search Kyle Sundqvist The Cryogenic Dark Matter Search (CDMS) seeks to detect putative weakly-interacting massive particles (WIMPS), which could explain the dark matter problem in cosmology and particle physics. By simultaneously measuring the number of charge carriers and the energy in athermal phonons created by particle interactions in intrinsic Ge and Si crystals at a temperature of $40 ~ mK$, a signature response for each event is produced. This response, combined with phonon pulse-shape information, allows CDMS to actively discriminate candidate WIMP interactions with nuclei apart from electromagnetic radioactive background which interacts with electrons. The challenges associated with these techniques are unique. Carrier drift-fields are maintained at only a few $V/cm$, else drift-emitted Luke-Neganov phonons would dominate the phonons of the original interaction. Under such conditions, carrier scattering is dominated by zero-point fluctuations of the lattice ions. It has been an open question how well the 8 Kelvin data prominent in the literature depicts this case. We compare the simulated transport properties of electrons and holes in $<100>$ Ge at $40~mK$ and at $8~K$, and apply this understanding to our detectors. [Preview Abstract] |
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