(a) $\mathrm{A}$ Si $\mathrm{p}^{+}-\mathrm{n}$ junction $10^{-2} \mathrm{~cm}^{2}$ in area has $N_{d}=10^{15} \mathrm{~cm}^{-3}$ doping on the $\mathrm{n}$ side. Calculate the junction capacitance with a reverse bias of $10 \mathrm{~V}$.
(b) An abrupt $\mathrm{p}^{+}-\mathrm{n}$ junction is formed in $\mathrm{Si}$ with a donor doping of $N_{d}=10^{15} \mathrm{~cm}^{-3} .$ What is the depletion region thickness $W$ just prior to avalanche breakdown?