Incoherent Transport in Nanowire - The Effect of Electron-phonon Interaction
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1206-M11-61
Incoherent Transport in Nanowire - The Effect of Electron-phonon Interaction. Hideyuki Nishizawa and Satoshi Itoh Functional Materials Lab., Toshiba Corporate R&D Center, Komukai Toshiba 1, Saiwai-Ku, Kawasaki, 212-8582, Japan. ABSTRACT The incoherent transport model based on electron-phonon interaction was introduced for calculating the current-voltage characteristics of the nanowire conductor. The current-voltage characteristics of silicon nanowire calculated based on this model was discussed. The charge transport was described by the rate equation containing the coherent (tunneling) and incoherent (energy dissipation) rates, and the incoherent rate was calculated from the Hamiltonian in which the electron-phonon interaction was incorporated. The coherent transition corresponds to the electronic transition between electrode states and channel states without any energy dissipation. On the other hand, the incoherent transition corresponds to the electronic transition between electrode states and channel states where the energy difference of those two states means a thermal dissipation. Therefore, in order to carry out the calculation by the rate equation, the density of states (DOSs) of the carriers in electrode and the channel and the DOS of the phonon in the channel are needed. The current-voltage characteristics were calculated by using the DOS of n-type semiconductor for the electrode and by using intrinsic semiconductor DOS for the channel. In addition, the calculation was performed by using the DOS of the silicon nanowire phonon. INTRODUCTION The one-dimensional semiconducting nanowire has attracted increasing interest in recent years for potential of new class field-effect transistors [2-7]. However, the research of the electrical property of the nanowire has not been sufficiently carried out. Generally, the atom vibrates easily to surface atom because the number of surrounding atoms is low. Therefore, the surface-phonon is different from the bulk-phonon. The interatomic distance change (lattice distortion) is large because of the change in the balance of Coulomb's force when the electron number changes. This means the electron-phonon interaction is large in the surface. The electron-phonon interaction should be large in nano-scale, because the atom in the nanostructure can be displaced easily as well as the surface atom. The electron-phonon interaction influences the charge transport process (for example Polaron transport). Because the effect is corresponding to an energy dispersion process by the phonon, the carrier transport becomes incoherent. Therefore, the incoherent transportation can be described by taking this effect. In this paper, the current in nano-structure was described by the rate equation to take into account of the effect of the electron-phonon interaction. In addition, the carrier exchange rate was calculated by using effective Hamiltonian that took the electron-phonon interaction energy. Finally, the current-voltage characteristics were calculated by using this rate equation.
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