schottky barrier

**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.