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Theoretical comparison of Si, Ge, and GaAs ultrathin p-type double-gate metal oxide semiconductor transistors
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Image of FIG. 1.
FIG. 1.

Top view of the considered Double-Gate p-type MOSFETs. For all devices,  = 2 nm,  = 1 nm, Source and Drain doping is 10 cm and ranges from 7 to 15 nm.

Image of FIG. 2.
FIG. 2.

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⟩. .

Image of FIG. 3.
FIG. 3.

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.

Image of FIG. 4.
FIG. 4.

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  = 10 nm.

Image of FIG. 5.
FIG. 5.

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.

Image of FIG. 6.
FIG. 6.

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.

Image of FIG. 7.
FIG. 7.

curves for various gate lengths of Si DG-pMOSFETs:  = 8 nm (squares),  = 9 nm (circles),  = 11 nm (triangles),  = 12 nm (reversed triangles), and  = 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. .

Image of FIG. 8.
FIG. 8.

curves for various gate lengths of Ge DG-pMOSFETs:  = 8 nm (squares),  = 9 nm (circles),  = 11 nm (triangles),  = 12 nm (reversed triangles), and  = 15 nm (diamonds). OFF currents decrease with channel length. ON current (inset) does not linearly vary with the channel length for . .

Image of FIG. 9.
FIG. 9.

Subthreshold slope (a) and (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 . This gate length value then characterizes the limit beyond which Ge devices have higher performances than their Si counterparts. .

Image of FIG. 10.
FIG. 10.

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. .


Generic image for table
Table I.

Principal material parameters used in this work for Si, Ge, and GaAs extracted from Refs. .


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Theoretical comparison of Si, Ge, and GaAs ultrathin p-type double-gate metal oxide semiconductor transistors