2-1. Schottky contact (Schottky junction) Φ_m > Φ_n

Let the work function of a metal be Φ_m and that of an n-type semiconductor be Φ_n. When Φ_m > Φ_n, a Schottky junction is formed when the n-type (or p-type) semiconductor is in contact with the metal. The Schottky junction is used to create Schottky barrier diodes. The following shows the band diagram of a Schottky junction formed by an n-type semiconductor and a metal.
As electrons move from a higher energy level to a lower energy level, they travel from the conduction band of the semiconductor to that of the metal. As a result, a depletion region extends only into the semiconductor side. As is the case with the pn junction, the Fermi level on the semiconductor side and that on the metal side match. In an equilibrium state, the junction has a diffusion barrier equal to the work function of the metal (Φ_m) minus that of the n-type semiconductor (Φ_n).
Free electrons are distributed across the n-type semiconductor according to the Fermi distribution. The electrons that cross the barrier of V_D flow into the metal.
Application of external voltage does not affect the barrier from the metal to the semiconductor, but causes the barrier from the semiconductor to the metal to shift by the applied voltage. This shift in the diffusion barrier causes a change in the current flowing through a Schottky barrier diode.