Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session W16: Semiconductor Applications |
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Sponsoring Units: FIAP Chair: James Levine, Kodak Room: Baltimore Convention Center 312 |
Thursday, March 16, 2006 2:30PM - 2:42PM |
W16.00001: Extraordinary Electrical Conductance in GaAs-In Hybrid Structures Yun Wang, K.A. Wieland, S.A. Solin Following the demonstration of extraordinary magnetoresistance (EMR)in semiconductor-metal hybrids\footnote{ S.A. Solin et al., Science {\bf289},1530 (2000).}, it has been realized that EMR is but one example of a general class of EXX phenomena that can be geometrically enhanced by the judicious choice of sample geometry. Two other EXX phenomena reported recently are extraordinary piezoconductance, EPC, and extraordinary Optoconductance, EOC. Here we address a fourth EXX phenomena, extraordinary electrical conductance, EEC. We develop a new design concept for an EEC sensor, which is a van der Pauw plate structure of Si-doped GaAs with a non-magnetic metallic shunt on top so that the external E field is perpendicular to the interface. EEC arises from the current redistribution between the shunt and GaAs when an external E field lowers the Schottky barrier at the interface. This allows more electrons to tunnel through and results in a larger conductance. We compare the response of a sample with a Schottky barrier to an unshunted sample and to a shunted sample with an Ohmic contact. The conductance of each sample was measured as a function of temperature, bias current and external perturbing field. In addition, we will compare the EEC structure to the Schottky diode structure to illustrate the advantages of an EEC sensor for static charge imaging. [Preview Abstract] |
Thursday, March 16, 2006 2:42PM - 2:54PM |
W16.00002: High-power mid-infrared interband cascade lasers Mijin Kim, Chul Soo Kim, Chadwick Canedy, William Bewley, James Lindle, Igor Vurgaftman, Jerry Meyer We have grown and fabricated interband cascade lasers (ICLs) with ``W'' active regions. The ICL structures were etched into 140-$\mu $m-wide ridges, with 100-$\mu $m-wide metal strips deposited in the middle, and operated epitaxial-side-up. Initial devices displayed lasing thresholds as low as 12 A/cm$^{2}$ at 78 K, series resistance as low as 0.21 m$\Omega \cdot $cm$^{2}$, and a voltage efficiency of 96{\%}. Cavity length studies on a series of ICLs with 5, 10, and 15 stages determined that the internal losses at 78 K were 16, 27, and 37 cm$^{-1}$, respectively, while the internal efficiencies were $\approx $ 80{\%} in all cases. Pulsed operating temperatures as high as 300 K were obtained, and a 5-stage device with 0.5 mm cavity length had a wallplug efficiency per facet of $\approx $ 20{\%} without facet coatings. A 3-mm-long laser with high-reflection (95{\%}) and anti-reflection (5{\%}) coatings produced $>$1.1 W of cw output power at 78 K. [Preview Abstract] |
Thursday, March 16, 2006 2:54PM - 3:06PM |
W16.00003: Single-Mode Distributed-Feedback ``W'' Diode and Interband Cascade Lasers in the Mid-Infrared Chul Soo Kim, Mijin Kim, Chadwick Canedy, William Bewley, James Lindle, Igor Vurgaftman, Jerry Meyer To obtain spectrally pure output, we have fabricated narrow index--guided ridges with lateral distributed-feedback (DFB) line gratings on both ``W'' diode and interband cascade lasers. The ``W'' diode structure containing a GaSb $p$-SCH etch-stop layer was chemically etched into a 5 $\mu $m ridge and a first-order DFB grating constructed on both side walls of the ridge. For the interband cascade laser, a first-order top DFB grating was patterned on top of a chemically-etched ridge that was 15 $\mu $m wide. The low-loss DFB mode was roughly resonant with the gain peak at $T$ = 165 K for the ``W'' diode and at $T$ = 110 K for the interband cascade laser. The sidemode suppression ratios were definitely $>$ 20 dB for both devices, and all of the features above 30 dB appeared to result from instrument noise rather than actual parasitic modes. Just beyond the stop band on the long-wavelength side of the ``W'' diode DFB, a series of longitudinal modes became apparent at $>$ 30 dB suppression. For the narrow-ridge waveguide DFB devices, the temperature ranges over which single-mode lasing were successfully obtained were 140-162 K for the ``W'' diode, for which $\lambda $ = 3.195 $\sim $ 3.202 $\mu $m (0.29 nm/K), and 110-125 K for the interband cascade laser, for which $\lambda $ = 3.452 $\sim $ 3.456 $\mu $m (0.27 nm/K). [Preview Abstract] |
Thursday, March 16, 2006 3:06PM - 3:18PM |
W16.00004: High Resolution 2D dopant profiling of FinFET structures and Silicon-based Devices using Scanning Probe Microscopies A. Khajetoorians, X.D. Wang, J. Li, D. Garcia-Gutierrez, J. Denyszyn, H. Celio, D. Pham, A. Diebold, J. Goodenough, M. Jose-Yacaman, C.K. Shih The ability to perform dopant/junction profiling with high spatial resolution is critical for development of future generation devices such as FinFET structures. Among various forms of scanning probe microscopy, scanning tunneling microscopy (STM) has demonstrated direct atomic imaging of dopant atoms on GaAs (110) surfaces. More recently, scanning thermoelectric microscopy (SThEM) (H.K. Lyeo et al \textit{Science} v.303 p816 (2004)) has been applied to profile GaAs $p-n$ junction with unprecedented spatial resolution. The key challenge to successfully apply these techniques to silicon-based devices is to prepare a surface that is both chemically and electronically passivated. Here we present our progress toward this goal. We present STM and SThEM studies on Si $p-n$ junction devices including FinFET structures. We also present in-depth profiling of fin structures using scanning capacitance (SCM) and conductive atomic force microscopy (C-AFM) (Khajetoorians \textit{et al} APL (submission)). [Preview Abstract] |
Thursday, March 16, 2006 3:18PM - 3:30PM |
W16.00005: Photoelectron Multipliers Based On Avalanche Pn-I-Pn Structures Hilda Cerdeira, Konstantyn Lukin, Pavel Maksymov We present a new optoelectronic device, which consists of a multilayered semiconductor structure, where the necessary conditions for the creation of photoelectrons are met, such that it will enable sequential avalanche multiplication of electrons and holes inside two depletion slabs created around the p-n junctions of a reverse biased pn-i-pn structure [1]. The mathematical model and computer simulations of this Semiconductor Photo-electron Multiplier (SPM) for different semiconductor materials are presented. Its performance is evaluated and later on compared with conventional devices. [1] K.A.Lukin, H.A.Cerdeira, A.A.Colavita, Current Oscillations in Avalanche Particle Detectors with pnipn-Structure. IEEE Transactions on Electron Devices. 43(3), 1996, 473-478. [Preview Abstract] |
Thursday, March 16, 2006 3:30PM - 3:42PM |
W16.00006: Electron relaxation through multiphonon processes in a double quantum dot Vasilios Stavrou, Xuedong Hu We theoretically study the relaxation of the electron orbital states of a double quantum dot system due to two-phonon processes. In particular, we calculate how the relaxation rates depend on the separation distance between the quantum dots, the strength of quantum dot confinement, and the lattice temperature. Our results show interesting crossovers in the relative strength of different scattering channels as temperature is varied. Furthermore, although at low temperatures two-phonon processes are much weaker compared to one-phonon processes in relaxing electron orbital states, at room temperature they are as important as one-phonon processes. [Preview Abstract] |
Thursday, March 16, 2006 3:42PM - 3:54PM |
W16.00007: Dark current generation in a confined and depleted region of silicon James Lavine, Daniel McGrath Dark current generation degrades the performance of silicon solid-state imagers. The present study examines whether a depleted region with defects supplies dark current to a photodiode when it is separated by a neutral region. Thermally-excited electron-hole pairs appear in the depleted region, which is confined by infinite potential barriers in two dimensions and a triangular potential well in the third. The triangular well has ground states of 0.036 and 0.058 eV for electric fields of 0.1 and 0.2 MV/cm, respectively. Lateral dimensions of 0.1 to 1.0 micrometers lead to high electron densities, which quench further dark current generation before excited states are occupied. As a result, the electrons must diffuse against the strong electric field and are unlikely to reach the photodiode. The same potential barrier accelerates the holes and creates electron-hole pairs by impact ionization. The electron would be generated near the top of the potential barrier. However, the probability that the hole acquires sufficient energy is 0.00001 for 0.2 MV/cm and 0.0028 for 0.3 MV/cm, based on J. S. Marsland in Solid-State Electronics 30, 125 (1987). If the defect is a gold atom at 55 C, this leads to 0.0056 and 1.6 electrons/s. [Preview Abstract] |
Thursday, March 16, 2006 3:54PM - 4:06PM |
W16.00008: Measuring Ionization and Athermal Phonons: Detectors of the Cyrogenic Dark Matter Search Kyle Sundqvist The Cryogenic Dark Matter Search (CDMS) is a search for weakly-interacting massive particles (WIMPS) in the halo of our galaxy. WIMPs are a favored solution to the dark matter problem in cosmology and particle physics. We will describe how CDMS measures simultaneously the number of charge carriers and the energy in athermal phonons created by particle interactions in Ge and Si crystals at a temperature of 50 mK. Together these distinct signals create a signature response for each event, allowing candidate WIMP interactions with nuclei to be discriminated from electromagnetic radioactive background which interacts with electrons. Combining this method with additional information contained in the athermal phonon signal shape, CDMS has achieved a sensitivity roughly ten times better than any other experiment in the world. These techniques introduce a number of unique challenges. Bias levels must remain at only a few volts, else the secondary phonons emitted by the drifted carriers dominate the original phonon signal. The neutralization of charge-trapping sites, even at concentrations of only $\sim10^{10}~ cm^{-3}$, is of primary importance to the performance of charge collection. We present the methods of crystal neutralization, subsequent characterization, and representative phenomena encountered in practice. [Preview Abstract] |
Thursday, March 16, 2006 4:06PM - 4:18PM |
W16.00009: Resistive all boron carbide neutron detectors Ellen Day, Manuel Diaz, Carolina Ilie, Shireen Adenwalla Semiconducting boron carbide is a promising material for true solid-state neutron detection [1]. An all boron carbide (BC) layer was deposited on sapphire (Al$_{2}$O$_{3})$ with sputtered Chrome/Gold electrical contacts. Resistance vs. temperature measurements indicate a T$^{-3/2}$ dependence and a band gap of $\sim $ 0.17eV. X-ray diffraction measurements confirm the similarities in crystal structure of the films grown on Al$_{2}$O$_{3}$ and Si. Detection area ranged from 0.25mm$^{2}$ to 1mm$^{2}$ and the thickness of the films ranged from 280nm to 600nm. Neutron detection measurements show no sharp spectral peaks but a long high energy tail which increased in counts as the reactor power was increased, in agreement with both monte carlo simulations and simple model calculations [2]. The low thermal neutron capture cross section of Al and O ensures that the entire neutron signal observed is from the resistive boron carbide layer, thus demonstrating the fabrication of an all boron carbide neutron detector. We show plots as a function of reactor power and thickness. [1] B.W. Robertson, S. Adenwalla, A. Harken, et al., \textit{Appl. Phys. Lett.} \textbf{80}, 3644 (2002). [2] C. Lundstedt, A. Harken, E. Day, B. W. Robertson, S. Adenwalla, submitted to NIM. [Preview Abstract] |
Thursday, March 16, 2006 4:18PM - 4:30PM |
W16.00010: What should neutron spectra from boron carbide devices look like? Carl Lundstedt, Ellen Day, Shireen Adenwalla GEANT4 (Geometry ANd Tracking) monte carlo modeling was performed on boron based neutron detectors [1]. Two different detector geometries were used. Geometry 1 consisted of a boron carbide (BC) layer placed on a Silicon (Si) layer in a cylindrical design with thermal neutrons of energy 0.025eV incident on the BC face. Geometry 2 was a rudimentary calorimeter made by sandwiching a moderator material between two BC/Si layers. The energy deposition spectra for the BC/Si device of various BC layer thicknesses for geometry 1 are presented as well as the spectra for geometry 2. In geometry 2, by changing the moderator material and thickness, higher energy neutrons may be detected, due to thermaization of neutrons in the moderator material. We show results for incident neutrons ranging in energy from 0.025eV to 2.5MeV. [1] C. Lundstedt, A. Harken, E. Day, B. W. Robertson, S. Adenwalla, submitted to NIM. [Preview Abstract] |
Thursday, March 16, 2006 4:30PM - 4:42PM |
W16.00011: Neutron detection characteristics of semiconducting boron carbide Andrew Harken, Brian Robertson The all boron carbide semiconducting neutron detector is sought because is could potentially yield the most useful and efficient of all thermal neutron detectors. We report on experiments to obtain data using alpha particle and neutron capture measurements. The results are analyzed in relation to our measurements of the dielectric properties and to initial charge transport considerations. The neutron capture results are compared with our modeling of the ideal neutron detector behavior calculated for an all boron carbide semiconductor device. [Preview Abstract] |
Thursday, March 16, 2006 4:42PM - 4:54PM |
W16.00012: Alpha-Energy-Deposition-Profiling of Radioisotope $p-i-n$ Diodes for Power Generation Cory Cress, Ryne Raffaelle The high energy density and long half-life of certain alpha-emitting radioisotopes enables viable and long-lived power supplies to be fabricated on the micro-scale. A design incorporating an InGaP $p-i-n$ photovoltaic (PV) device that directly converts the kinetic energy of the alpha-particles into electricity represents both a scalable and efficient microsystem design. To better understand the relationship between the alpha-energy-deposition-profile (ADEP) and the maximum power conversion efficiency for this device structure, we have performed two systematic studies. In these studies, I-V characteristics for the InGaP PV device under alpha-flux are measured as a function of alpha source distance, and as function of aluminum film thickness (10 nm to 10 $\mu $m) which is deposited onto the surface of the PV device. Both techniques will alter the ADEP in relation to the active region of the PV device. These experimental results are compared to a theoretical model which utilizes Monte Carlo simulations and numerical calculations to determine the ADEP for the same device configuration. The understanding gained from this analysis has direct implications towards the fabrication of radioisotope microbatteries with structural characteristics that enable optimal power conversion efficiencies to be achieved. [Preview Abstract] |
Thursday, March 16, 2006 4:54PM - 5:06PM |
W16.00013: Analysis of microwave-frequency field patterns in an externally-driven Single-Electron Transistor Bryan Hemingway, Andrei Kogan We report a numerical study of electromagnetic field patterns that emerge in a Single-Electron Transistor (SET) device driven by a microwave-frequency signal. In an SET, an electronic droplet (quantum dot) containing a few electrons is connected to two macroscopic conductors via tunnel barriers, and DC current measurements are used to investigate the quantum properties of the lead-dot system. Our goal is to develop a method for a well-controlled excitation of few-electron devices with microwaves. Such capability is needed for investigating the intrinsic time scales of Kondo-correlated electrons, not accessible in static experiments. We study realistic model geometry of an SET defined lithographically on a semiconductor heterostructure such as GaAs/AlGaAs. We find that at frequencies $\sim $ 10 GHz and above, the microwave voltages across the sub-micron features of the SET can be drastically different from those applied to the large-scale pads and depend in a complex and sensitive way on the excitation frequency, thus presenting a challenge for dynamic transport experiments with SETs. We discuss possible strategies for resolving the problem. [Preview Abstract] |
Thursday, March 16, 2006 5:06PM - 5:18PM |
W16.00014: The effect of negative electron affinity emitter materials on space charge mitigation of vacuum thermionic energy conversion devices Joshua Smith, Griff Bilbro, Robert Nemanich Vacuum thermionic energy conversion (TEC) devices provide a way to convert heat directly into electrical work. The negative space charge effect has been an effect that significantly degrades the performance of these devices, requiring small interelectrode spacings for reasonable performance. Recently, Nitrogen doped, Hydrogen terminated, ultra-nanocrystalline diamond films have been investigated as possible candidates for low operating temperature, low work function emitter materials. Furthermore, these materials exhibit a so-called negative electron affinity (NEA) where the vacuum level lies below the conduction band minimum of the material. As a result of this NEA property, the distribution of thermionically emitted electrons will have some nonzero minimum initial velocity. A model was developed to determine the effect that the NEA property of these types of emitters have on mitigation of the space charge effect. The model shows that a TEC with an NEA emitter material will have comparable performance with a non-NEA emitter TEC with a smaller gap. Thus, it is possible to use NEA emitters to relax the requirement of a small gap distance. [Preview Abstract] |
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