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Lecture Notes_20-22_MOS_2014

In this slide cox is the oxide capacitance per unit

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Unformatted text preview: s the permittivity in free space. We call Koxεo = εox here. The electric field in the semiconductor decreases linearly to zero because the space charge is constant (constant doping) and the electric field is zero at and outside the depletion region. At the particular gate bias for the left figure, the positive oxide charge is balanced by the negative metal charge and the negative space charge in the depletion region. When the gate bias is more negative to a point when there is no depletion region, we reach the flat- band condition, that is, no charges in the semiconductor. The flat- band voltage VFB is just the product of the electric field in the oxide εo times the 25 26 27 distance of the oxide charge from the metal xo. From Gauss’ Law in E&M, εo = Qo/εox. Capacitance per unit area Cox is εox/d, where...
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