Definition of Schottky diode

Photonics Dictionary

Schottky diode: A Schottky diode is a type of semiconductor diode characterized by its low forward voltage drop and fast switching speed. It is formed by the junction of a metal and an n-type semiconductor, creating a Schottky barrier rather than a p-n junction.

Structure: A Schottky diode consists of a metal-semiconductor junction. Common metals used include platinum, palladium, gold, and certain silicides, while the semiconductor is typically silicon, though gallium arsenide and other materials can also be used.

Schottky barrier: At the metal-semiconductor interface, an energy barrier known as the Schottky barrier is formed. This barrier controls the movement of electrons and creates the diode's rectifying behavior.

Forward voltage drop: Schottky diodes have a lower forward voltage drop (typically between 0.15 to 0.45 volts) compared to conventional p-n junction diodes (which typically have a forward voltage drop of about 0.7 volts for silicon diodes). This lower forward voltage drop results in higher efficiency, especially in low voltage applications.

Fast switching speed: Schottky diodes can switch on and off much faster than p-n junction diodes. This makes them suitable for high-speed and high-frequency applications, such as in switching power supplies and RF circuits.

Current-voltage characteristics: The current through a Schottky diode increases exponentially with forward bias voltage, similar to a p-n junction diode, but with a lower threshold voltage. Under reverse bias, the diode exhibits low reverse leakage current, although typically higher than that of a p-n junction diode.

Applications:

Power rectification: Used in power supplies and rectifier circuits to convert AC to DC with higher efficiency.

RF applications: Employed in RF mixers and detectors due to their fast response time.

Clamping and protection: Used in circuits to protect against voltage spikes and to clamp voltages.

Solar cells: Integrated in photovoltaic systems for better efficiency in converting sunlight to electricity.

Advantages:

Efficiency: Low forward voltage drop leads to lower power loss and higher efficiency.

Speed: Fast switching characteristics are ideal for high-speed and high-frequency applications.

Limitations:

Reverse leakage current: Higher reverse leakage current compared to p-n junction diodes can be a drawback in applications where low leakage current is crucial.

Voltage ratings: Generally, Schottky diodes have lower maximum voltage ratings compared to p-n junction diodes, which limits their use in high-voltage applications.

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