Green Transistor - A V&lt;inf&gt;DD&lt;/inf&gt; Scaling Path for Future Low Power ICs

Hu, Chenming; Chou, Derek; Patel, Preet; Bowonder, Anupama

doi:10.1109/vtsa.2008.4530776

Cited by 47 publications

(37 citation statements)

References 4 publications

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“…17). Only E g was reduced in simulation, not any other tunneling parameters [1]. At E g =0.36eV I ON exceeds 1mA/µm at V DD =0.2V with CV/I=0.4pS and can operate well at 0.1V (Fig.…”

Section: Iedm10-388mentioning

confidence: 94%

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Prospect of tunneling green transistor for 0.1V CMOS

Patel

Bowonder

et al. 2010

2010 International Electron Devices Meeting

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Well designed tunneling green transistor may enable future VLSIs operating at 0.1V. Sub-60mV/decade characteristics have been convincingly demonstrated on 8" wafers. Large I ON at low V DD are possible according to TCAD simulations but awaits verification. V DD scaling will greatly benefit from low (effective) band gap energy, which may be provided by type II heterojunctions of Si/Ge or compound semiconductors.A Looming Barrier to IC Scaling Reducing the voltage V DD is a powerful way to reduce IC energy consumption, which is proportional to V DD 2 . Power usage was kept under control when V DD was reduced in proportion to half-pitch up to 130nm as shown in Fig 1 [1]. The 14nm node is projected to operate at 0.7V, making the power consumption 25x larger than it would be if operated at 0.14V as the past trend suggests. While IC power consumption has been much discussed as a thermal management challenge, it is also responsible for a few percent of the electricity usage and growing fast. MOSFET current cannot rise faster than one decade for every 60mV increase in V g (the subthreshold swing, SS). To reduce V DD to 0.14V with I ON /I OFF ratio of mere 3 decades, SS needs to be 45mV/decade. A low voltage transistor (Green Transistor, gFET) is needed.Green Transistor with Steep Turn On/Off In MOSFETs (and BJTs), a potential barrier is raised and lowered by V g to turn the current on and off (Fig. 2). Due to Boltzmann distribution, some electrons always have sufficient energy to pass over the barrier. The current can only be reduced by the rate of electron density drop with increasing energy, hence the 60 mV/decade limit [1]. To beat this limit, the carriers must not flow over a barrier. They may tunnel through it. Fig. 3 shows a prototype tunnel transistor [1][2][3][4]. Electrons are generated by band-to-band tunneling in the P+ source when the gate voltage bends the energy band to satisfy two conditions-overlap of the valence and conduction bands and the a high electric field or thin tunnel barrier [5]. The generated electrons flow through the surface N-channel to the drain. Fig. 4 shows simulated I d -V g [6] assuming uniform source doping. In all > 3E19 cm -3 cases, steep turn on occurs at the onset of band overlap. Unfortunately the graded source doping profile and the averaging effect of the Poisson equation provide a continuous range of (effective) doping concentration near the tip of the source. At points of lower doping (Fig. 4) the turn-on voltages and electric field (therefore I ON ) are both lower. The envelope of these curves is the IV of a prototype tunnel transistor, with a disappointing sub-V t swing.

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“…17). Only E g was reduced in simulation, not any other tunneling parameters [1]. At E g =0.36eV I ON exceeds 1mA/µm at V DD =0.2V with CV/I=0.4pS and can operate well at 0.1V (Fig.…”

Section: Iedm10-388mentioning

confidence: 94%

“…Fig. 3 shows a prototype tunnel transistor [1][2][3][4]. Electrons are generated by band-to-band tunneling in the P+ source when the gate voltage bends the energy band to satisfy two conditions-overlap of the valence and conduction bands and the a high electric field or thin tunnel barrier [5].…”

Section: Introductionmentioning

confidence: 99%

Prospect of tunneling green transistor for 0.1V CMOS

Patel

Bowonder

et al. 2010

2010 International Electron Devices Meeting

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“…One of the most promising devices is a tunneling field-effect transistor (TFET) [1][2][3][4][5][6][7][8][9][10]. TFETs are expected to achieve low power consumption because they have a subthreshold swing less than 60 mV/dec at room temperature and lower off-current than MOSFETs.…”

Section: Introductionmentioning

confidence: 99%

Ambipolarity Factor of Tunneling Field-Effect Transistors (TFETs)

Jang¹,

Choi²

2011

JSTS:Journal of Semiconductor Technology and Science

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Abstract-The ambipolar behavior of tunneling fieldeffect transistors (TFETs) has been investigated quantitatively by introducing a novel parameter: ambipolarity factor (ν). It has been found that the malfunction of TFET can result from the ambipolar state which is not on-or off-state. Therefore, the effect of ambipolar behavior on the device performance should be parameterized quantitatively, and this has been successfully evaluated as a function of device structure, gate oxide thickness, supply voltage, drain doping concentration and body doping concentration by using ν.

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“…By switching the tunneling mechanism to a vertical approach characterized by an enhancement of the gate-induced drain Manuscript leakage present in MOSFETs, it is possible to increase the tunneling area of TFETs proportionally to their gate length and to obtain large ON currents. Such a vertical TFET design has been recently proposed [7]- [9] and named "green FET" (gFET) for its potential to reduce the supply voltage of transistors.…”

Section: Introductionmentioning

confidence: 99%

Leakage-Reduction Design Concepts for Low-Power Vertical Tunneling Field-Effect Transistors

Agarwal

Klimeck

Luisier

2010

IEEE Electron Device Lett.

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Using an atomistic full-band quantum transport solver, we investigate the performances of vertical band-to-band tunneling FETs (TFETs) whose operation is based on the enhancement of the gate-induced drain leakage mechanism of MOSFETs, and we compare them to lateral p-i-n devices. Although the vertical TFETs offer larger tunneling areas and therefore larger ON currents than their lateral counterparts, they suffer from lateral source-to-drain tunneling leakage away from the gate contact. We propose a design improvement to reduce the OFF current of the vertical TFETs, maintain large ON currents, and provide steep subthreshold slopes.Index Terms-Band-to-band tunneling transistors, full-band and atomistic quantum transport, steep subthreshold.

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Green Transistor - A V<inf>DD</inf> Scaling Path for Future Low Power ICs

Cited by 47 publications

References 4 publications

Prospect of tunneling green transistor for 0.1V CMOS

Prospect of tunneling green transistor for 0.1V CMOS

Ambipolarity Factor of Tunneling Field-Effect Transistors (TFETs)

Leakage-Reduction Design Concepts for Low-Power Vertical Tunneling Field-Effect Transistors

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