申論題

MOS capacitor and MOSFET
5.Assumed that there is an Al/ SiO₂/ p -Si metal-oxide-semiconductor (MOS) capacitor. Denote the permittivity of SiO₂ (Si) as and it is given that the thickness of SiO2 is , the p-Si is uniformly doped to N_A, and the MOS capacitor can be regarded as one-dimensional.

(a) Given that the work function of the Al is slightly larger than , the electron affinity of Si, and assumed that the oxide is perfect (completely insulating, no fixed charge/interface states within the oxide and at the interface), please plot the band diagrams of the MOS capacitor when the MOS capacitor is biased at equilibrium and threshold, respectively. You have to include (vacuum level), Ec (conduction band edge), Ei (intrinsic level) , Ev (valence band edge) and E_F (Fermi level) in you plots. Please also indicate on you plot the condition that the MOS structure reaches threshold. (10%)