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Homework Help: How to draw the energy band diagram for a semiconductor-oxide-semicondutor structure?

  1. Sep 24, 2009 #1
    1. The problem statement, all variables and given/known data
    A schematic diagram of a silicon-oxide-silicon structure is shown. The top and bottom silicon electrodes are uniformly doped. The top silicon electrode is N-type and its dopant concentration is 2E16 cm-3. The bottom silicon electrode is p-type and its dopant concentration is 1E16cm-3. The oxide layer is 30nm thick and free from defects. The bottom electrode is always grounded and a voltage can be applied to the top electrode.

    Pls draw the energy diagram when zero bias is applied to the top electrode.

    2. Relevant equations
    We are taught how to draw the energy diagram for a metal-oxide-semiconductor structure. In this question, we are asked to draw a SOS structure.

    3. The attempt at a solution
    Since the Fermi level at n-type is higher than that at p-type, the electrons will fly to p-type to make the Fermi levels at the two sides flat. Then the conduction band and valence band will bend upwards at p-type silicon as well as the oxide. But I do not know whether I should draw the two band bending or not at n-type semicondutor. I checked the reference books for MOSFET structure. If the gate is n+ poly-si, they never draw bending at the gate side.

    Pls help, really do not know whether need to bend or not at the n-type silicon side. Thanks a lot
  2. jcsd
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