A Silicon PN junction diode under reverse bias has depletion region of width $10 \; \mu \mathrm{m}$. The relative permittivity of Silicon,$\varepsilon_{r}=11.7$ and the permittiveity of free space $\varepsilon_{0}=8.85 \times 10^{-12} \mathrm{~F/m}$. The depletion capacitance of the diode per square meter is
- $100 \; \mu \mathrm{F}$.
- $10 \; \mu \mathrm{F}$.
- $1 \; \mu \mathrm{F}$.
- $20 \; \mu \mathrm{F}$.