We present a first-principles model to study tunnel transistors based on van der Waals heterojunctions of 2D materials in the presence of dissipative mechanisms due to the electron-phonon interaction. To this purpose we employed a reduced basis set composed of unit-cell restricted Bloch functions computed with a plane wave ab-initio solver and performed self-consistent quantum transport simulations within the non-equilibrium Green’s functions formalism. Phonon scattering was included with specific self-energies making use of the deformation potential approximation for the electron-phonon coupling. Our simulations identify the van der Waals tunnel FET as a promising option to attain high on-state currents at low supply voltages, but also show a strong impact of the phonon scattering on the transport properties of such device in the sub-threshold regime.
We present a first-principles model to study tunnel transistors based on van der Waals heterojunctions of 2D materials in the presence of dissipative mechanisms due to the electron-phonon interaction. To this purpose we employed a reduced basis set composed of unit-cell restricted Bloch functions computed with a plane wave ab-initio solver and performed self-consistent quantum transport simulations within the Non-equilibrium Green's functions formalism. Phonon scattering was included with specific self-energies making use of the deformation potential approximation for the electron-phonon coupling. Our simulations identify the van der Waals tunnel FET as a promising option to attain high on-state currents at low supply voltages, but also show a strong impact of the phonon scattering on the transport properties of such device in the sub-threshold regime.
Two-dimensional (2D) ferroelectric (FE) materials are
promising
compounds for next-generation nonvolatile memories due to their low
energy consumption and high endurance. Among them, α-In2Se3 has drawn particular attention due to its in-
and out-of-plane ferroelectricity, whose robustness has been demonstrated
down to the monolayer limit. This is a relatively uncommon behavior
since most bulk FE materials lose their ferroelectric character at
the 2D limit due to the depolarization field. Using angle resolved
photoemission spectroscopy (ARPES), we unveil another unusual 2D phenomenon
appearing in 2H α-In2Se3 single crystals,
the occurrence of a highly metallic two-dimensional electron gas (2DEG)
at the surface of vacuum-cleaved crystals. This 2DEG exhibits two
confined states, which correspond to an electron density of approximately
1013 electrons/cm2, also confirmed by thermoelectric
measurements. Combination of ARPES and density functional theory (DFT)
calculations reveals a direct band gap of energy equal to 1.3 ±
0.1 eV, with the bottom of the conduction band localized at the center
of the Brillouin zone, just below the Fermi level. Such strong n-type
doping further supports the quantum confinement of electrons and the
formation of the 2DEG.
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