Work Function and Barrier Formation

3. Work Function and Barrier Formation

The work function (Φ) of a material represents the minimum energy required to remove an electron from its surface. Metals generally have a higher work function than n-type semiconductors. Schottky diode  .When a metal with a higher work function is brought into contact with an n-type semiconductor, electrons from the semiconductor are attracted to the metal. This causes a depletion of electrons near the semiconductor surface, creating a positively charged region known as the depletion region.

Simultaneously, a negative charge accumulates on the metal side of the interface. As a result, an electrostatic potential barrier, the Schottky barrier, is established at the metal-semiconductor interface. The height of this barrier,

4. Forward Biasing and Current Conduction

When a Schottky diode is forward-biased, an external voltage is applied such that the anode (connected to the metal) is made positive with respect to the cathode (connected to the n-type semiconductor). This applied voltage opposes the built-in Schottky barrier. As the forward voltage increases and reaches a certain threshold (usually around 0.3 - 0.5 volts for silicon-based Schottky diodes, much lower than the 0.7 volts for silicon p-n junction diodes), the barrier height is reduced significantly.

Once the barrier is sufficiently lowered, electrons from the n-type semiconductor can easily overcome the barrier and flow into the metal. This flow of electrons constitutes the forward current of the Schottky diode. Since the current in a Schottky diode is mainly due to the majority carriers (electrons in the n-type semiconductor), there is no significant charge storage effect as in p-n junction diodes. This absence of minority carrier storage enables Schottky diode to switch on and off rapidly, making them ideal for high-frequency applications.