1,721,135 research outputs found
Formation of axial metal-semiconductor junctions in GaAs nanowires by thermal annealing
No full textWe demonstrate the formation of nanoscale axial Schottky contacts in GaAs nanowires by thermal annealing of NiGeAu multilayers. Energy dispersive x-ray spectroscopy indicates that in specific annealing conditions a sharply-defined Au-rich phase can be obtained in the vicinity of the metallic contacts. Charge transport characteristics are analyzed for different degrees of diffusion of the Au-rich phase in the wire and indicate that it has a metallic nature. The mechanism behind this local post-growth modification of the nanowire composition and its potential impact on device applications are discussed
Manipulation of Electron Orbitals in Hard-Wall InAs/InP Nanowire Quantum Dots RID C-6303-2008
No full textWe present a novel technique for the manipulation of the energy, spectrum of hard wall InAs/InP nanowire quantum dots. By using two local gate electrodes, we induce a strong transverse electric field in the dot and demonstrate the controlled modification of its electronic orbitals. Our approach allows us to dramatically enhance the single particle energy spacing between the first two quantum levels in the dot and thus to increment the working temperature of our InAs/InP single electron transistors. Our devices display a very robust modulation of the conductance even at liquid nitrogen temperature, while allowing an ultimate control of the electron filling down to the last free carrier. Potential further applications of the technique to time-resolved spin manipulation are also discussed
Rectification and Photoconduction Mapping of Axial Metal-Semiconductor Interfaces Embedded in GaAs Nanowires
Full text linkSemiconductor nanowires have emerged as an important enabling technology and are today used in many advanced device architectures, with an impact both for what concerns fundamental science and in view of future applications. One of the key challenges in the development of nanowire-based devices is the fabrication of reliable nanoscale contacts. Recent developments in the creation of metal-semiconductor junctions by thermal annealing of metallic electrodes offer promising perspectives. Here, we analyze the optoelectronic properties of nano-Schottky barriers obtained thanks to the controlled formation of metallic AuGa regions in GaAs nanowire. The junctions display a rectifying behavior and their transport characteristics are analyzed to extract the average ideality factor and barrier height in the current architecture. The presence, location, and properties of the Schottky junctions are cross-correlated with spatially resolved photocurrent measurements. Broadband light emission is reported in the reverse breakdown regime; this observation, combined with the absence of electroluminescence at forward bias, is consistent with the device unipolar nature
Manipulation of Electron Orbitals in Hard-Wall InAs/InP Nanowire Quantum Dots
No full textWe present a novel technique for the manipulation of the energy spectrum of hard-wall InAs/InP nanowire quantum dots. By using two local gate electrodes, we induce a strong transverse electric field in the dot and demonstrate the controlled modification of its electronic orbitals. Our approach allows us to dramatically enhance the single-particle energy spacing between the first two quantum levels in the dot and thus to increment the working temperature of our InAs/InP single-electron transistors. Our devices display a very robust modulation of the conductance even at liquid nitrogen temperature, while allowing an ultimate control of the electron filling down to the last free carrier. Potential further applications of the technique to time-resolved spin manipulation are also discussed
Contacts shielding in nanowire field effect transistors
No full textConductive metallic contacts can significantly affect the operation of field effect transistors fabricated starting from semiconductor nanowires deposited on a dielectric substrate. Screening effects can also lead to systematic errors in the estimates of transport parameters obtained on the basis of simple uniform capacitive models. We study the role of contacts in both back- and lateral-gate transistor geometries and provide rules of thumbs to predict screening effects in real devices. Additionally, we show how the contacts influence charge density profiles within the wire, focusing in particular on their evolution when transistors nonlinear properties are addressed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3693027
Electrostatic spin control in multi-barrier nanowires
No full textWe demonstrate that a consistent breakdown of the standard even–odd filling scheme in the Coulomb blockade regime can be easily obtained in a quantum dot containing two wells strongly coupled by a very transparent barrier. By exploiting a multi-gate configuration, we prove that a partial filling of nearly degenerate orbitals can be controlled electrostatically. Singlet–triplet spin transitions are demonstrated by low-temperature magneto-transport measurements
Interedge strong-to-weak scattering evolution at a constriction in the fractional quantum Hall regime
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