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A silicon $n$ $\text{MOSFET}$ has a threshold voltage of $1$ $\mathrm{V}$ and oxide thickness of $\mathrm{AO}$.

$\left[\varepsilon_{r}\left(\mathrm{siO}_{2}\right)=3.9, \varepsilon_{\mathrm{o}}=8.854 \times 10^{-14} \mathrm{~F} / \mathrm{cm}\right.$, $\left.q=1.6 \times 10^{-19} \mathrm{C}\right]$

The region under the gate is ion-implanted for threshold voltage tailoring. The dose and type of the implant (assumed to be a sheet charge at the interface) required to shift the threshold voltage to $-1 \mathrm{~V}$ are

- $1.08 \times 10^{12} / \mathrm{cm}^{2}, p$-type
- $1.08 \times 10^{12} / \mathrm{cm}^{2}, n$-type
- $5.4 \times 10^{11} / \mathrm{cm}^{2}, p$-type
- $5.4 \times 10^{11} / \mathrm{cm}^{2}, n$-type