An n-channel MOS transistor is made on a p-type substrate with Na = $$10^{15} cm^{-3}$$ Find approximate depletion charge per unit area $$(Q_{d})$$ at strong inversion.
$$\left\{\ln(10)=2.3,\sqrt{0.046} \approx 0.215, n_{i}=10^{10} cm^{-3}\right\}$$

A

$$-6.9 \times 10^{-8}  C/cm^2$$

B

$$6.9 \times 10^{-8}  C/cm^2$$

C

$$-3.4 \times 10^{-8}   C/cm^2$$

D

$$3.4 \times 10^{-8}   C/cm^2$$