Investigation of Performance Limits of Germanium Double-Gated MOSFETs

Tony Low, Y. T. Hou, M. F. Li, Chunxiang Zhu, Albert Chin, G. Samudra, L. Chan, D. L. Kwong

Research output: Contribution to journalConference article

45 Citations (Scopus)

Abstract

The performance limits and engineering issues of ultra-thin body (UTB) double gated (DG) Ge channel n-MOSFETs are examined in this paper. The non-equilibrium Green's Function (NEGF) approach, including both L and Δ conduction valleys, is employed for source to drain current, while the improved WKB tunneling is employed for substrate to drain (band-to-band BTB) and gate to channel current. All possible Ge surfaces and channel orientations are explored. In terms of drive current I ON, highly anisotropic Ge〈110〉 channel exhibits highest I ON which increases with body thickness scaling; Ge〈100〉 exhibits similar ballistic limit as Si〈100〉 due to increasing Δ valley carrier dominance at UTB regime; Ge〈111〉exhibits higher ballistic limit but decrease at UTB regime due to the small density-of-states mass of L valley. Sub-threshold slope is worse for Ge〈110〉 and Ge〈111〉 as channel length is scaled down. In terms of standby current I OFF and gate leakage I G for low standby power (LSTP) devices, BTB tunneling is large due to the small energy gap of Ge. This imposes a limit on maximum tolerable supply voltage (of which Ge〈111〉 is worst and Ge〈100〉 is best) thus requiring low voltage operation. Body scaling is effective in suppressing BTB tunneling, since carrier quantization causes effective energy gap widening. The low voltage requirement demands small EOT for minimal oxide voltage drop. However, gate leakage will impose a limit for further EOT scaling, of which Ge 〈110〉 is worst and Ge〈111〉 is best. Our results conclude that in addition to lower power supply voltage advantage, the engineered Ge〈110〉 devices with suppressed BTB and gate leakages can achieve better intrinsic delay to OFF power ratio than Si〈100〉 devices.

Original languageEnglish (US)
Pages (from-to)691-694
Number of pages4
JournalTechnical Digest - International Electron Devices Meeting
StatePublished - Dec 1 2003
EventIEEE International Electron Devices Meeting - Washington, DC, United States
Duration: Dec 8 2003Dec 10 2003

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Germanium
thin bodies
germanium
field effect transistors
Electric potential
valleys
Ballistics
leakage
Energy gap
scaling
low voltage
ballistics
electric potential
Drain current
Green's function
Oxides
power supplies
Green's functions
engineering
slopes

Cite this

Low, T., Hou, Y. T., Li, M. F., Zhu, C., Chin, A., Samudra, G., ... Kwong, D. L. (2003). Investigation of Performance Limits of Germanium Double-Gated MOSFETs. Technical Digest - International Electron Devices Meeting, 691-694.

Investigation of Performance Limits of Germanium Double-Gated MOSFETs. / Low, Tony; Hou, Y. T.; Li, M. F.; Zhu, Chunxiang; Chin, Albert; Samudra, G.; Chan, L.; Kwong, D. L.

In: Technical Digest - International Electron Devices Meeting, 01.12.2003, p. 691-694.

Research output: Contribution to journalConference article

Low, T, Hou, YT, Li, MF, Zhu, C, Chin, A, Samudra, G, Chan, L & Kwong, DL 2003, 'Investigation of Performance Limits of Germanium Double-Gated MOSFETs', Technical Digest - International Electron Devices Meeting, pp. 691-694.
Low, Tony ; Hou, Y. T. ; Li, M. F. ; Zhu, Chunxiang ; Chin, Albert ; Samudra, G. ; Chan, L. ; Kwong, D. L. / Investigation of Performance Limits of Germanium Double-Gated MOSFETs. In: Technical Digest - International Electron Devices Meeting. 2003 ; pp. 691-694.
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abstract = "The performance limits and engineering issues of ultra-thin body (UTB) double gated (DG) Ge channel n-MOSFETs are examined in this paper. The non-equilibrium Green's Function (NEGF) approach, including both L and Δ conduction valleys, is employed for source to drain current, while the improved WKB tunneling is employed for substrate to drain (band-to-band BTB) and gate to channel current. All possible Ge surfaces and channel orientations are explored. In terms of drive current I ON, highly anisotropic Ge〈110〉 channel exhibits highest I ON which increases with body thickness scaling; Ge〈100〉 exhibits similar ballistic limit as Si〈100〉 due to increasing Δ valley carrier dominance at UTB regime; Ge〈111〉exhibits higher ballistic limit but decrease at UTB regime due to the small density-of-states mass of L valley. Sub-threshold slope is worse for Ge〈110〉 and Ge〈111〉 as channel length is scaled down. In terms of standby current I OFF and gate leakage I G for low standby power (LSTP) devices, BTB tunneling is large due to the small energy gap of Ge. This imposes a limit on maximum tolerable supply voltage (of which Ge〈111〉 is worst and Ge〈100〉 is best) thus requiring low voltage operation. Body scaling is effective in suppressing BTB tunneling, since carrier quantization causes effective energy gap widening. The low voltage requirement demands small EOT for minimal oxide voltage drop. However, gate leakage will impose a limit for further EOT scaling, of which Ge 〈110〉 is worst and Ge〈111〉 is best. Our results conclude that in addition to lower power supply voltage advantage, the engineered Ge〈110〉 devices with suppressed BTB and gate leakages can achieve better intrinsic delay to OFF power ratio than Si〈100〉 devices.",
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AU - Low, Tony

AU - Hou, Y. T.

AU - Li, M. F.

AU - Zhu, Chunxiang

AU - Chin, Albert

AU - Samudra, G.

AU - Chan, L.

AU - Kwong, D. L.

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N2 - The performance limits and engineering issues of ultra-thin body (UTB) double gated (DG) Ge channel n-MOSFETs are examined in this paper. The non-equilibrium Green's Function (NEGF) approach, including both L and Δ conduction valleys, is employed for source to drain current, while the improved WKB tunneling is employed for substrate to drain (band-to-band BTB) and gate to channel current. All possible Ge surfaces and channel orientations are explored. In terms of drive current I ON, highly anisotropic Ge〈110〉 channel exhibits highest I ON which increases with body thickness scaling; Ge〈100〉 exhibits similar ballistic limit as Si〈100〉 due to increasing Δ valley carrier dominance at UTB regime; Ge〈111〉exhibits higher ballistic limit but decrease at UTB regime due to the small density-of-states mass of L valley. Sub-threshold slope is worse for Ge〈110〉 and Ge〈111〉 as channel length is scaled down. In terms of standby current I OFF and gate leakage I G for low standby power (LSTP) devices, BTB tunneling is large due to the small energy gap of Ge. This imposes a limit on maximum tolerable supply voltage (of which Ge〈111〉 is worst and Ge〈100〉 is best) thus requiring low voltage operation. Body scaling is effective in suppressing BTB tunneling, since carrier quantization causes effective energy gap widening. The low voltage requirement demands small EOT for minimal oxide voltage drop. However, gate leakage will impose a limit for further EOT scaling, of which Ge 〈110〉 is worst and Ge〈111〉 is best. Our results conclude that in addition to lower power supply voltage advantage, the engineered Ge〈110〉 devices with suppressed BTB and gate leakages can achieve better intrinsic delay to OFF power ratio than Si〈100〉 devices.

AB - The performance limits and engineering issues of ultra-thin body (UTB) double gated (DG) Ge channel n-MOSFETs are examined in this paper. The non-equilibrium Green's Function (NEGF) approach, including both L and Δ conduction valleys, is employed for source to drain current, while the improved WKB tunneling is employed for substrate to drain (band-to-band BTB) and gate to channel current. All possible Ge surfaces and channel orientations are explored. In terms of drive current I ON, highly anisotropic Ge〈110〉 channel exhibits highest I ON which increases with body thickness scaling; Ge〈100〉 exhibits similar ballistic limit as Si〈100〉 due to increasing Δ valley carrier dominance at UTB regime; Ge〈111〉exhibits higher ballistic limit but decrease at UTB regime due to the small density-of-states mass of L valley. Sub-threshold slope is worse for Ge〈110〉 and Ge〈111〉 as channel length is scaled down. In terms of standby current I OFF and gate leakage I G for low standby power (LSTP) devices, BTB tunneling is large due to the small energy gap of Ge. This imposes a limit on maximum tolerable supply voltage (of which Ge〈111〉 is worst and Ge〈100〉 is best) thus requiring low voltage operation. Body scaling is effective in suppressing BTB tunneling, since carrier quantization causes effective energy gap widening. The low voltage requirement demands small EOT for minimal oxide voltage drop. However, gate leakage will impose a limit for further EOT scaling, of which Ge 〈110〉 is worst and Ge〈111〉 is best. Our results conclude that in addition to lower power supply voltage advantage, the engineered Ge〈110〉 devices with suppressed BTB and gate leakages can achieve better intrinsic delay to OFF power ratio than Si〈100〉 devices.

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