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4. Suppose we have an nMOSCAP made of Si. Suppose the channel doping is too strong at 10¹⁹ cm³³. All plots should assume the metal is on the left side. For this problem, we apply Vgs = Vth. (a) Plot metal and depletion region charge densities. Label local extrema and depletion region edges. Hint: what polarity of charge exists on the metal with a positive voltage? (b) Plot electric field; positive values mean pointing to the right. Label local extrema and depletion region edges. Warning: oxide permittivity > Si permittivity. (c) Plot electric potential, assuming the source is grounded. Label local extrema and depletion region edges.

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