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Field effect transistors question

  1. Mar 20, 2015 #1
    [ Mod note: moved from Elec Eng, might have better luck here]

    I have some basic knowledge of how FET work. But i have a question that i can't see the answer.

    For example:

    In a MOSFET we have a p-doped Silicon substrate. Then we have two n-doped silicons, with a oxide layer above the the p-doped Silicon substrate.

    When we increase the gate voltage, we are creating a n-type channel between the n-doped silicons (called the inversion layers). The more we increase the gate voltage the more electrons can move in the n type channel.

    My question is, why in the recent papers, the new 2D semiconductors, like metal transition dichalcogenides, are used as n type channel?

    What is their function? They increase the carriers mobility inside the channel?
  2. jcsd
  3. Mar 23, 2015 #2
    The 2D semiconductor IS the channel.
  4. Mar 24, 2015 #3


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    Staff: Mentor

    I believe the member understands that. As I read it, the question centres on why the use of "metal transition dichalcogenides".
  5. Mar 24, 2015 #4
    Your question is confusing...
  6. Apr 16, 2015 #5
    Yes the SC is the channel. But how does it works?

    Suppose the we have a MOSFET with n-type semiconductor channel. Like the one that you can seei in link below.


    We apply a negative bias in gate, so it going to repel the electrons in n-type channel semiconductor. What is the objective of repelling the electrons? Does this repelling works like the depletion (repelling it is going to reduce the width of the channel)?

    And if we apply a positive bias in gate. We are accommodating electrons in the interface (n-type semiconductor channel and oxide). Whats the point of this?
    Last edited: Apr 16, 2015
  7. Apr 17, 2015 #6


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    Science Advisor

    They talk about a tunnel effect FET. Did you check their ref. 19, which seems to contain a description of the mechanism?
  8. Apr 17, 2015 #7
    For what i see, the tunneling effects can explain the transport of electrons from the source to the n type semiconductor.

    But what i don't understand is the mechanism of the capacitor metal-dielectric-ntype SC. I dont see how can we create any depletion here. And how can we induce electrons in the channel? when the channel has already the electrons?

    Im my head, we have a ntype semiconductor without any electron in conduction band (ideal situation). If we apply the field effect, then we are giving enough energy to electrons to transit for the conduction band. Now that we have electrons in the conduction band (thinking of it as an inversion layer), we can control the current with the depletion at the drain.

    I know that his is wrong, but i cant see its mechanism.
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