Physics of Semiconductor Devices

Depletion width in a MOS capacitor

In a silicon MOS capacitor, the silicon is doped p-type at N_a = 4000000000000000 cm^-3. Inversion occurs when the applied gate voltage is 2eφ_F. What is the depletion width at 300 K?

For Si: n_i = 1.5 × 10¹⁰ cm³, ε_r = 11.9.