Consider an abrupt PN junction (at $T = 300 K$) shown in the figure. The depletion region width $X_{n}$ on the $N$-side of the junction is $0.2 \mu m$ and the permittivity of silicon $( \varepsilon _{gi} )$ is $1.044 \times 10^{-12} \: F/cm$. At the junction, the approximate value of the peak electric field (in $kV/cm$) is ___________.