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I How is a top gate used to change electron density?

  1. May 18, 2016 #1
    How is a top gate used to change electron density in 2D semi conductors?

    I get the principle, you are just shifting the chemical potential by some voltage so that there are more or less electrons in the specific bands. But how is it physically done?

  2. jcsd
  3. May 19, 2016 #2
    I think generation of higher voltage can be done 1) with carrier source or 2) by an electric filed. Both viewpoints give the same result:
    1) A region with higher voltage (such a gate) includes more density of electrons provided by a source, in other words, Fermi level is higher there. In contact with a semiconductor, electrons diffuse into it.
    2) In a region with higher potential, the bands are shifted up (due to an electric field) and so do the electrons. Hence, Fermi energy is higher compared to the next region which causes diffusion.
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