Utente:Giulio.galderisi/Sandbox

RFET

RFET

The reconfigurable field effect transistor (RFET), also known as polarity-control Schottky barrier field effect transistor (PC-SBFET), is a field effect transistor whose conduction mechanism can be reconfigured between n-type (electron conduction) and p-type (hole conduction). Such a device enables to have both functionalities, that are usually realized by two different devices, in only one. This kind of device is usually controlled by at least two independent gates: one is used to select the kind of charge carrier (electrons or holes) and the second one modulates the conductance of the channel and so the amount of current (i.e. carriers per time unit). Multiple gate architectures have been proposed for devices with enhanced functionalities.

The first reconfigurable device was proposed by Lin et al. in 2004 through the use of a carbon nanotube (CNT) with a double gating structure capable of selecting the carrier type and modulating the amount of current flowing inside the carbon nanotube. In the recent years many materials have been used to realize this kind of device, ranging from mature technologies like FinFETs and FDSOI substrates to more research-oriented materials like nanowires (silicon and germanium) to 2D materials.

History (materials anche qua dentro, non troppo)

Yu-Ming Lin, Joerg Appenzeller and Phaedon Avouris proposed the first implementation of a reconfigurable field effect transistor in 2004 at the IBM T.J. Watson Research Center. They used a carbon nanotube as channel material, exploiting the exceptional transport properties of such nanostructured material that was arising in those years.

More Moore & More Than Moore (forse dopo non qua)

Here, I would like to discuss about how the RFET can be placed in the middle of the two approaches, combining both device scaling and functionalization. Here it should be highlighted very strongly the reconfigurability feature as a mean to reach a perfect combination of the two approaches.

E.g. Cutting edge electronics is currently seeking for new strategies in order to keep realizing Moore´s scaling law. Eventually the physical limit of scaling will be reached and so industry has adopted an alternative strategy beside continuing scaling (Moore More), i.e. producing devices with improved functionalities (Moore than Moore).  In the middle it can be found a lot of space for reasonably down scaled devices with improved functionalities. RFET can be attributed to this category since it is a nanometric device with both n and p functionalities.

Physics

From now on I would talk about the device in a more "technical way", describing the basic physics principles upon which the device operations are based.

Schottky Contacts

Here is important to provide a first introduction to the physics of the Schottky contacts.

Schottky Barrier FET (SB-FET)

Extending the previous paragraph it would useful to present this device, highlighting the advantages but also the strong limitations.

also talk about the need for symmetry as a requirement for the rfet in comparison with the sbfet

Working Principles of RFET

Here the device should be introduced, with the explanation of how it works and what are the different ways to operate it (indipendent gates, common back gate, etc...). It should be introduced the importance of the Si/NiSi interface for the precise control of the carrier injection at the Schottky barrier (to be better explained in the fabrication section).

Now the different concepts of RFETs should be presented.

Independent SB Gating

(PG and CG as independent TGs) ...

Dependent SB Gating with Channel Barrier Tuning

(PG as BG and CG as TG, PG as two dependent TGs and CG as independent third TG) ...

Ambipolar Operations

(Just explain the operation when a voltage is swept at the BG) ...

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At some point here it should be introduced the issue about barrier height for electrons and holes. In the fabrication section it would be possible to explain the solution based on stress applied by oxidation.

Fabrication (part of the history)

Bottom-up vs top-down technologies, also citing first namlab papers with respect with the former. Reconnecting to the importance of a sharp interface at the nanoscale, here the importance of the Si-NW has to be highlighted. Also the fact that the material is still Si should be considered as a strong advantage.

Here one should talk of all the important technological challanges like the precise control of the silicidation, the gate coupling efficiency (omega gate, tri gate, 2DMs, ...).

Here also Ge-NWs can be cited. In the next section, also electrical characteristics could be compared.

Electrical Characteristics with band diagrams and different type of operations

Here we should provide information about the electrical characteristics of such devices (swing, on/off ratios, I_max, I_min, symmetry, etc...). Also a table comparing the results of all the proposed devices could be nice to show.

Table.X Electrical Characteristics of various proposed RFETs

	Swing	On/Off	........	........	........
VV.AA. 19XX
VV.AA 20XX
...
...
VV.AA. 201X

Comparison with Other Electronic Devices (meglio vantaggi che confronto)

Here I would compare the RFET with "more classic" devices, such as MOSFET, considering both technological features and performances.

Applications

Reconfigurable circuits for logic, hardware security , gate reconfiguration dynamic gate (sbfet che funziona bene non so se serve la riconfigurazione) (cerca), temperature stability (cerca), non-volatile devices, etc...

dire da qualche parte che la corrente e generalmente bassa ( come problema del dispositivo), area consuption for additonal gate. Materiale con minore bandgap per risolvere il problema della bassa crrente (Ge, or 2d material con low bandgap).

References

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