Top view of the considered Double-Gate p-type MOSFETs. For all devices, TSC = 2 nm, TOX = 1 nm, Source and Drain doping is 1020 cm–3 and LG ranges from 7 to 15 nm.
characteristics without (squares) and with hole-phonon scattering (circles) in Si-based transistor, both in semi-logarithmic (left) and linear scale (right). The gate-length is 10 nm and the channel orientation is along ⟨100⟩. .
Current density spectrum along the transport direction for , and in ⟨100⟩-Si DG pMOSFET. Inelastic scattering due to optical-phonons gives rise to phonon absorptions on the source side and phonon emissions on the drain side. Electrostatic potential is sketched in thick black line. The current spectrum follows its shape due to relaxations.
characteristic comparisons between ⟨100⟩ (squares) and ⟨110⟩ (circles) oriented pMOSFETs with Si (a), Ge (b) and GaAs (c) as channel material. For all three materials, ⟨100⟩ transistors exhibit higher performances than their ⟨110⟩ counterparts. and LG = 10 nm.
Bandstructures of 2 nm thick Si layer along the ⟨100⟩ (plus sign) and ⟨110⟩ (cross sign) directions, extracted from the six-band k.p Hamiltonian. The differences between the first two subbands in each direction are found to provide better electrical characteristics for ⟨100⟩-based pMOSFETs. Similar features are found for Ge and GaAs.
characteristics of ⟨100⟩-oriented 7 nm gate-length transistors with Ge (squares), Si (circles) and GaAs (triangles) as channel material. Si represents the best material for this gate length. and hole-phonon scattering is included.
curves for various gate lengths of Si DG-pMOSFETs: LG = 8 nm (squares), LG = 9 nm (circles), LG = 11 nm (triangles), LG = 12 nm (reversed triangles), and LG = 15 nm (diamonds). As expected, the OFF currents decrease with channel length. ON currents are also decreasing due to stronger hole-phonon interactions as shown in the inset. .
curves for various gate lengths of Ge DG-pMOSFETs: LG = 8 nm (squares), LG = 9 nm (circles), LG = 11 nm (triangles), LG = 12 nm (reversed triangles), and LG = 15 nm (diamonds). OFF currents decrease with channel length. ON current (inset) does not linearly vary with the channel length for . .
Subthreshold slope (a) and ION (b) in Ge (squares) and Si (circles) pMOSFETs as a function of gate length. For , the same SS are obtained in both devices while Ge still provides higher ION . This gate length value then characterizes the limit beyond which Ge devices have higher performances than their Si counterparts. .
characteristics of Ge (squares), Si (circles), and GaAs-based (triangles) pMOSFETs for a channel's length of 15 nm, (a) with and (b) without phonons. We show the importance of considering phonon interactions since ballistic current characteristics do not clearly exhibit the predominance of Ge for this dimension. .
Principal material parameters used in this work for Si, Ge, and GaAs extracted from Refs. 20–22 .
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