On experimental determination of carrier velocity in deeply scaled NMOS: how close to the thermal limit?

Lochtefeld, A.; Antoniadis, D.A.

doi:10.1109/55.902843

Cited by 150 publications

(85 citation statements)

References 10 publications

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“…The gate insulator in our current devices is un-optimized and thicker than the channel length. It will be feasible to integrate high κ dielectrics such as ZrO 2 9 into SWNT-contacted molecular FETs to afford ~10-fold increase in C G and therefore further enhance the electrostatic gate control. With quasi-1D contacts, gate scaling could allow for organic transistors approaching the limit of S ~ 60 mV/decade.…”

Section: B Cmentioning

confidence: 99%

Miniature Organic Transistors with Carbon Nanotubes as Quasi-One-Dimensional Electrodes

et al. 2004

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With a cut metallic SWNT (gap L ~ 5-6 nm) bridged by a pentacene nano-crystallite (Fig.1b&c), we observed clear semiconducting FET characteristics in the current vs. gate (I ds -V gs ) curve (Fig. 2a). The device exhibited a current modulation of I max /I min ~ 10 5 under gating at a fixed bias voltage of V ds = -0.5V. The drastic switching clearly differed from the original metallic SWNT device (lack of gate dependence, Fig. 2a inset). This corresponds to the formation of a pentacene FET with channel length L ~ 5-6 nm and width of w ~ 2 nm (i.e., the diameter of the SWNT) as charge transport via hopping between pentacene molecules should be mainly confined in a width on the order of the tube diameter. Notably, the subthreshold swing of the device is S ~ 400 mV/decade (Fig. 2a).Small organic molecules and conjugated polymers can be easily processed to afford functional electronics such as field effect transistors (FETs), 1a and in principle, scaling 1b to singlemolecule long devices could circumvent the low carrier mobility problem for these materials to afford high performance ballistic FETs 2,3 . For highly scaled molecular transistors with short channels however, it is crucial to develop novel device geometries to optimize gate electrostatics needed for ON/OFF switching. 4,5 It is shown here that single-walled carbon nanotubes (SWNT) can be used as quasi one-dimensional (1D) electrodes to construct organic FETs with molecular scale width (~2 nm) and channel length (down to 1-3 nm). The favorable gate electrostatics associated with the sharp 1D electrode geometry allows for room temperature conductance modulation by orders of magnitude for organic transistors that are only several-molecules in length, with switching characteristics superior to devices with lithographically patterned metal electrodes. We suggest that carbon nanotubes may prove to be novel electrodes for a variety of molecular devices.We first developed a reproducible method of cutting metallic SWNTs to form small gaps within the tubes and with control over the gap size down to L~2 nm. The cutting relied on electrical break-down 6 of individual SWNTs between two metal electrodes (Fig. 1a), and the size of the cut was found to be controllable by varying the lengths of the SWNTs (see Ref.6b and Supp. Info). Organic materials were then deposited to bridge the gap in the vapor (for pentacene) or solution phase (for regio-regular ploy (3-hexylthiophene), P3HT), forming the smallest organic FETs with effective channel length down to L~1-3 nm and width ~2 nm. b cWe varied the channel lengths L of SWNT-contacted pentacene FETs (L ~ 1-3 nm, L ~5-6 nm and L ~10-15 nm respectively) and observed length dependent transport properties at various temperatures. At T=300K, the devices exhibited on-current I max scaling approximately with ~1/L (under V ds =-1 V). This suggests

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Section: B Cmentioning

confidence: 99%

Miniature Organic Transistors with Carbon Nanotubes as Quasi-One-Dimensional Electrodes

et al. 2004

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“…To this purpose, in [4] the BR is extracted by comparing the product Q inv v inj with I D , where Q inv is obtained by C/V measurements and v inj is estimated by means of simulations. The method in [1,5], instead, evaluates r directly from the variations of I D and of the threshold voltage V T with temperature.…”

Section: Introductionmentioning

confidence: 99%

On the experimental determination of channel back-scattering in nanoMOSFETs

Zilli

Palestri

Esseni

et al. 2007

2007 IEEE International Electron Devices Meeting

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By using accurate Multi-Subband-Monte-Carlo simulations of quasi-ballistic transport we carry out a detailed re-examination of the experimental extraction procedure for the ballistic-ratio BR=I D /I BAL in nanoMOSFETs proposed in [1]. It is found that the ballistic-ratio extracted applying this procedure to the simulated drain current severely underestimates the BR extracted by directly compare the simulated I D and I BAL . This is mainly due to inaccurate determination of the temperature dependence of the inversion charge. It is suggested that this limitation of the extraction procedure may explain the apparent lack of improvement in the ballisticity with the geometrical scaling [1,5,13,14]. IntroductionThe back-scattering coefficient (r) [2,3] where (see Fig.1) Q inv and v inj are the inversion charge density and the average velocity of the injected carriers at the virtual source (VS), L kT is the extension of the kT-layer and µ 0 is the low-field mobility. Extraction procedure for BR.As described in [1], by taking the derivative with respect to the temperature T of the expressions in Eq.1, and assuming power-laws with exponent γ µ , γ vinj and γ lkt for the T dependence of µ 0 , v inj and L kT respectively, one gets:that becomes (using Eq.1):where α=∆I D /(I D ∆T ) and β=∆Q inv /(Q inv ∆T ). The parameter α can be measured directly, whereas β is more difficult to estimate, since Q inv needs to be sampled at the virtual source. In [1] it is a priori assumed that: γ µ =−1.5, γ vinj =0.5, γ lkt =1 and β=−η/(V GS −V T ), where η=∆V T /∆T . This set of parameters is denoted as set A in the following. 105 1-4244-0439-X/07/$25.00

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“…Consider first the charge at the virtual source. It can be estimated from experiment C−V (long channel) from [38,39] …”

Section: Charge Control In a Nanoscale Hemtmentioning

confidence: 99%

Device Physics and Performance Potential of III-V Field-Effect Transistors

Liu

Pal²,

Lundstrom³

et al. 2010

Fundamentals of III-V Semiconductor MOSFETs

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The device physics and technology issues for III-V transistors are examined from a simulation perspective. To examine device physics, an InGaAs HEMT structure similar to those being explored experimentally is analyzed. The physics of this device is explored using detailed, quantum mechanical simulations based on the non-equilibrium Green's function formalism. In this chapter, we: (1) elucidate the essential physics of III-V HEMTs, (2) identify key technology challenges that need to be addressed, and (3) estimate the expected performance advantage for III-V transistors. IntroductionDriven by tremendous advances in lithography, the semiconductor industry has followed Moore's law by shrinking transistor dimensions continuously for the last 40 years. The big challenge going forward is that continued scaling of planar, silicon, CMOS transistors will be more and more difficult because of both fundamental limitations and practical considerations as the transistor dimensions approach ten nanometers. The issues at small gate lengths are many fold. First, transistor scaling increases the number of gates on a chip and the operating frequency. To prevent the chip from overheating, the power dissipation should be limited, which requires lowering the power supply voltage while maintaining the ability to deliver high oncurrents for each new generation of technology. Secondly, the drain bias decreases the energy barrier height between the source and channel in a transistor due to 2D electrostatics. Degraded short channel effects become more significant as the gate length gets shorter, and the increased off-state leakage has pushed the standby power to its practical limit. Thirdly, the accompanying scaled oxide thickness provides better gate control of the channel potential, but this inevitably increases S. Oktyabrsky, P. D. Ye (eds.), Fundamentals of III-V Semiconductor MOSFETs,

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On experimental determination of carrier velocity in deeply scaled NMOS: how close to the thermal limit?

Cited by 150 publications

References 10 publications

Miniature Organic Transistors with Carbon Nanotubes as Quasi-One-Dimensional Electrodes

Miniature Organic Transistors with Carbon Nanotubes as Quasi-One-Dimensional Electrodes

On the experimental determination of channel back-scattering in nanoMOSFETs

Device Physics and Performance Potential of III-V Field-Effect Transistors

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