Schottky Barrier is the potential energy barrier that forms at the interface between a metal and a semiconductor — determined by the difference between the metal work function and the semiconductor electron affinity, governing current flow (rectification, ohmic contact, or tunneling).

What Is a Schottky Barrier?

• Height ($Phi_B$): $Phi_B = Phi_m - chi_s$ (ideal case). $Phi_m$ = metal work function, $chi_s$ = semiconductor electron affinity.
• Fermi Level Pinning: In reality, surface states pin $Phi_B$ near mid-gap regardless of the metal used (especially on Si).
• Current Transport: Thermionic emission (over the barrier), Thermally-assisted tunneling, Direct tunneling (high doping).

Why It Matters

• Contact Resistance: Lower $Phi_B$ -> lower contact resistance. This is why Ti and TiN are preferred for NMOS contacts.
• Schottky Diodes: Used as fast-switching devices (no minority carrier storage -> fast recovery).
• S/D Engineering: Achieving $Phi_B < 0.1$ eV is critical for sub-5nm node contact resistance.

Schottky Barrier is the quantum entrance fee at the metal-semiconductor interface — the energy barrier that electrons must overcome to cross between the metal and the chip.