Direct and Indirect Band-to-Band Tunneling in Germanium-Based TFETs

Kao, Kuo-Hsing; Verhulst, Anne S.; Vandenberghe, William G.; Sorée, Bart; Groeseneken, G.; Meyer, K. De

doi:10.1109/ted.2011.2175228

Cited by 411 publications

(196 citation statements)

References 31 publications

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“…The required change of momentum of the tunneling particle here occurs via phonon absorption/emission while no phonon is required in direct Γ Γ band-to-band tunneling, which significantly increases the tunneling probability. Recent simulations 3 indicate that Ge and GeSn, 4 which offer much lower bandgaps and smaller carrier effective masses, boost the Tunnel-FET performance due to an increased contribution of direct transitions. 5 While the bandgap engineered III/V heterostructures for Tunnel-FETs have been theoretically and experimentally investigated, 6 Si based direct bandgap TunnelFETs still lack of suitable materials for their realization.…”

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confidence: 99%

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Band engineering and growth of tensile strained Ge/(Si)GeSn heterostructures for tunnel field effect transistors

Wirths

Tiedemann

Ikonić

et al. 2013

Applied Physics Letters

147

109

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Abstract:In this letter, we propose a heterostructure design for tunnel field effect transistors with two low direct bandgap group IV compounds, GeSn and highly tensely strained Ge in combination with ternary SiGeSn alloy. Electronic band calculations show that strained Ge, used as channel, grown on Ge 1-x Sn x (x>9%) buffer, as source, becomes a direct bandgap which significantly increases the tunneling probability. The SiGeSn ternaries are well suitable as drain since they offer a large indirect bandgap. The growth of such heterostructures with the desired band alignment is presented. The crystalline quality of the (Si)Ge(Sn) layers is similar to state-of-the-art SiGe layers.

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confidence: 99%

“…The idea is to exploit the properties of two direct bandgap group IV semiconductors, GeSn and tensely strained Ge, as source and channel, respectively, in combination with an indirect 3 SiGeSn alloy as drain. The calculated electronic band diagram for such a structure is shown in Fig.…”

mentioning

confidence: 99%

Band engineering and growth of tensile strained Ge/(Si)GeSn heterostructures for tunnel field effect transistors

Wirths

Tiedemann

Ikonić

et al. 2013

Applied Physics Letters

147

109

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“…Simulation results of GeSn and Ge TFETs show that the direct BTBT dominates the total tunneling current. 21,23,33 The direct G BTBT values along [110] parallel and [001] perpendicular to channel direction are calculated, as shown in Fig. 10.…”

Section: B Gesn Ptfets: Impact Of Uniaxial Tensile Strainmentioning

confidence: 99%

Relaxed germanium-tin P-channel tunneling field-effect transistors fabricated on Si: impacts of Sn composition and uniaxial tensile strain

Han¹,

Wang²,

Liu³

et al. 2015

AIP Advances

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In this work, relaxed GeSn p-channel tunneling field-effect transistors (pTFETs) with various Sn compositions are fabricated on Si. Enhancement of on-state current ION with the increase of Sn composition is observed in transistors, due to the reduction of direct bandgap EG. Ge0.93Sn0.07 and Ge0.95Sn0.05 pTFETs achieve 110% and 75% enhancement in ION, respectively, compared to Ge0.97Sn0.03 devices, at VGS - VTH = VDS = - 1.0 V. For the first time, ION enhancement in GeSn pTFET utilizing uniaxial tensile strain is reported. By applying 0.14% uniaxial tensile strain along [110] channel direction, Ge0.95Sn0.05 pTFETs achieve 12% ION improvement, over unstrained control devices at VGS - VTH = VDS = - 1.0 V. Theoretical study demonstrates that uniaxial tensile strain leads to the reduction of direct EG and affects the reduced tunneling mass, which bring the GBTBT rising, benefiting the tunneling current enhancement in GeSn TFETs.

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“…1 9 Ge also has a direct band gap at the L-point that is 0.14 eV larger than the indirect band gap at the C-point in the E-K diagram. 10 Moreover, theoretical studies show that under high gate electric field, direct tunneling dominates in Ge, as well as, in Si 1-x Ge x with high Ge mole fraction (x ! 0.8) due to the slightly larger direct band gap in Ge.…”

Section: Introductionmentioning

confidence: 99%

“…0.8) due to the slightly larger direct band gap in Ge. 10 Therefore, engineering the Si/Ge hetero-structure to include an overlap with the gate would potentially induce higher band-to-band tunneling (BTBT) rate due to vertical tunneling within the Ge source where electrons tunnel within the source region in the direction perpendicular to the semiconductor/ gate-dielectric interface. 11 Vertical tunneling is more desirable as it allows for a controlled cross sectional area for tunneling controlled by the gate-to-source overlap, where electrons are injected from within the source area to the inverted surface region of the source (in the source-to-gate overlap region).…”

Section: Introductionmentioning

confidence: 99%

Si/Ge hetero-structure nanotube tunnel field effect transistor

Hanna

Hussain

2015

Journal of Applied Physics

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We discuss the physics of conventional channel material (silicon/germanium hetero-structure) based transistor topology mainly core/shell (inner/outer) gated nanotube vs. gate-all-around nanowire architecture for tunnel field effect transistor application. We show that nanotube topology can result in higher performance through higher normalized current when compared to nanowire architecture at Vdd = 1 V due to the availability of larger tunneling cross section and lower Shockley-Reed-Hall recombination. Both architectures are able to achieve sub 60 mV/dec performance for more than five orders of magnitude of drain current. This enables the nanotube configuration achieving performance same as the nanowire architecture even when Vdd is scaled down to 0.5 V.

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Direct and Indirect Band-to-Band Tunneling in Germanium-Based TFETs

Cited by 411 publications

References 31 publications

Band engineering and growth of tensile strained Ge/(Si)GeSn heterostructures for tunnel field effect transistors

Band engineering and growth of tensile strained Ge/(Si)GeSn heterostructures for tunnel field effect transistors

Relaxed germanium-tin P-channel tunneling field-effect transistors fabricated on Si: impacts of Sn composition and uniaxial tensile strain

Si/Ge hetero-structure nanotube tunnel field effect transistor

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