A Semiconductor with Embedded Nanoparticles Invisible to the Conduction Carriers

Technology #15799

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A schematic cross-sectional view of a scattering center particle having a core material region that produces a potential barrier, and a shell material region that produces a potential well, in a host material in which the particle is disposed and an electron wave is traveling;FIG. 5A is a plot of prespecified scattering potential produced by the core and scattering potential produced by the shell of the scattering center particle of FIG. 2A, corresponding to choices for a range of core and shell radii; FIG. 5B is a plot of scattering center cross sections as a function of electron energy for the core-shell scattering center particle of FIG. 2A for each in a range of core effective masses;FIG. 6 is a plot of scattering cross section as a function of Fermi energy, which is the incident energy of electrons traveling in a host material, defining a prespecified Fermi level energy at which the scattering cross section is minimized, and defining a range of Fermi level energies at which the scattering cross section is minimized; FIG. 7A is a plot of scattering rate as a function of Fermi level energy for resonance scattering and for anti-resonance scattering; FIGS. 7B-7D are plots of the electrical conductivity, Seebeck coefficient, and power factor, for the resonance and anti-resonance conditions of the plot of FIG. 7A; FIG. 8A is a plot of the scattering cross section as a function of electron energy for the core-shell scattering center particle of FIG. 2A, for the first two partial waves and the total of their contributions, of an electron wave traveling in a host material in which the particle is disposed, for the particle parameters given for Z=1 in Table I; FIG. 8B is a plot of the electrical potential of the scattering center particle for which the cross section is plotted in FIG. 8A, as a function of distance through the particle
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Inventors
Professor Gang Chen
Department of Mechanical Engineering, MIT
External Link (web.mit.edu)
Keivan Esfarjani
Department of Mechanical Engineering, MIT
Bolin Liao
Department of Mechanical Engineering, MIT
Mona Zebarjadi
Department of Mechanical Engineering, MIT
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

SOLID STATE CLOAKING FOR ELECTRICAL CHARGE CARRIER MOBILITY CONTROL

US Patent 9,076,712
Publications
Cloaking Core-Shell Nanoparticles from Conducting Electrons in Solids
American Physical Society, Sept. 20, 2012, Phys. Rev. Lett. 109, 126806

Applications

This technology can be used to create highly conductive transistors, diodes, and metal–oxide–semiconductor field-effect transistor (MOSFETs). It can also be implemented in very precise electronic switches and filters.

Problem Addressed

Currently, semiconductors are doped to increase carrier density and, theoretically, electrical conductivity. However, doping also increases the carrier scattering cross section which decreases electrical conductivity. The proposed method increases carrier mobility and decreases carrier scattering cross section for a desired energy window. The separation of these properties allows the electrical conductivity and the thermoelectric figure-of-merit to simultaneously increase.

Technology

The key to this design is fabricating carrier donating nanoparticles with a specific potential profile to minimize the electron scattering cross section within the Fermi window, cloaked nanoparticles, to guarantee mobility enhancement. If the scattering cross section versus energy has a large slope at the edges of the Fermi window, anti-resonance scattering, the thermoelectric power factor also increases significantly.  This is done by using core-shell structured nanoparticles - modeled as two-step potential wells - and only modifying the barrier height and well depth. Using this technique a residue scattering cross section smaller than 0.01% of the physical cross section was observed. More remarkably, 4 orders of magnitude difference in total scattering cross section was presented within an energy range of only 40meV. This invention makes it possible to design scattering centers with anti-resonance or cloaking features in a specifically tunable energy range. Using these techniques, materials with almost perfect carrier transmission can be designed. Similarly, an electronic filter is created by tuning the specific energy range and the on-off scattering ratio so only charge carriers in a specific energy range will pass. Finally, by controlling the on-off scattering ratio, proper switches can be designed and used for quantum information storage.

Advantages

  • Simultaneous increase of electrical conductivity and thermoelectric figure-of-merit
  • Ability to create precise electronic filters and switches