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Germanium-tin n-channel tunneling field-effect transistor: Device physics and simulation study
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10.1063/1.4805051
/content/aip/journal/jap/113/19/10.1063/1.4805051
http://aip.metastore.ingenta.com/content/aip/journal/jap/113/19/10.1063/1.4805051

Figures

Image of FIG. 1.
FIG. 1.

(a) Composition dependence of Ge Sn band-gap at Γ-valley ( ) and -valley () for Ge Sn alloy. Symbols are experimental data and the lines are obtained from EPM calculations. For Ge Sn alloys with Sn composition below 0.11, the conduction band minimum is at -point, and the alloy is an indirect band-gap material. For higher than 0.11, Ge Sn is a direct band-gap material since the conduction band minimum is located at Γ-point. (b) Full band dispersion for Ge and GeSn. As Sn composition increases, Ge Sn alloy transits from indirect to direct band-gap at around  = 0.11. The differences in band-gaps at Γ-point and -point are highlighted as Δ and Δ.

Image of FIG. 2.
FIG. 2.

(a) The DOS electron effective mass in the -valley ( ) is larger than the one in the Γ-valley ( ) for Ge Sn alloys with various (b) The intrinsic carrier concentration and electron occupation ratio versus Sn composition. For Ge Sn with  > 0.11, although the conduction band minimum at the Γ-valley is lower than the one at the -valley, there are more electrons in -valley than Γ-valley.

Image of FIG. 3.
FIG. 3.

Tunneling reduced masses for Γ-Γ BTBT ( ) and Γ- BTBT ( ) decrease as Sn composition increases.

Image of FIG. 4.
FIG. 4.

(a) Schematic showing device structure of DG Ge Sn TFET. (b) Band diagram near surface along -axis of GeSn TFET at  =  = 0.3 V. Since is lower than , the tunneling distance from at the source side to in the channel (denoted by gray arrow) is shorter than that from at the source side to in the channel (denoted by black arrow). (c) Band diagram near surface along -axis of GeSn TFET at  =  = 0.3 V. Since is lower than , is shorter than .

Image of FIG. 5.
FIG. 5.

Spatial distributions of (a) , (b) , and (c) for GeSn TFET at  =  = 0.3 V. As the double-gate device is symmetrical about a mirror line at  = 12.5 nm, only the upper half body (0 <  < 12.5 nm) is shown.

Image of FIG. 6.
FIG. 6.

Spatial distributions of (a) , (b) , and (c) for GeSn TFET at  =  = 0.3 V. As the double-gate device is symmetrical about a mirror line at  = 12.5 nm, only the upper half body (0 <  < 12.5 nm) is shown. The magnitude of for GeSn TFET is larger than that for GeSn TFET shown in Fig. 5(c) .

Image of FIG. 7.
FIG. 7.

(a) Simulated - for GeSn TFET. is lower than since is smaller than . As is larger than , BTBT from at source side to occurs. However, at  > , BTBT from to dominates the tunneling current. (b) Simulated - for GeSn TFET. is lower than since is smaller than . As  > , BTBT occurs from at source side to and dominates the drive current once reaches .

Image of FIG. 8.
FIG. 8.

(a) A set of - curves of Ge Sn TFETs with ranging from 0 to 0.2. (b) Point versus for Ge Sn TFETs with from 0 to 0.2. For GeSn TFET, sub-60 mV/decade is achieved at a high current level of ∼8 A/m.

Image of FIG. 9.
FIG. 9.

versus of Ge Sn TFETs with  = 0.00, 0.05, 0.08, 0.11, and 0.17 at a supply voltage of 0.3 V. For a given , is the value of when equals to the , is extracted at  =  = 0.3 V. is varied from 10 to 10 mA/m. For a fixed , of Ge Sn TFET is higher than that of Ge TFET.

Tables

Generic image for table
Table I.

Summary of material parameters used in TCAD simulation.

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/content/aip/journal/jap/113/19/10.1063/1.4805051
2013-05-20
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Germanium-tin n-channel tunneling field-effect transistor: Device physics and simulation study
http://aip.metastore.ingenta.com/content/aip/journal/jap/113/19/10.1063/1.4805051
10.1063/1.4805051
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