Schottky Diode and its working

Schottky Diode

What is Schottky Diode?

Schottky diode

Schottky Diode is constructed by joining N type  semiconductor material and a metal electrode together. The junction of semiconductor and the metal is called Schottky barrier. This diode is named after the German Physicist Walter H. Schottky. This diode has a low forward voltage drop and switches over very fastly.

Symbol of Schottky diode:

Symbol of Schottky diode

Construction of Schottky diode :

Construction of Schottky diode

This figure shows the construction of lighty doped N type semiconductor and metal electrode joined together forming metal semiconductor junction. The metals used are molybdenum, platinum, tungsten or chromium and the semiconductor used is only N type material. Normally Gallium semiconductor is used and silicon is used in low frequency applications. Metal side is Anode and N type semiconductor is Cathode.

Schottky barrier:

Schottky barrier

The junction formed by joining the N type semiconductor and the metal is called as Schottky barrier. The electrons have to overcome this potential barrier when external voltage is applied, for the current to flow.

 

Working of Schottky diode:

  

Forward bias of Schottky diode

When external voltage is applied when forward biased electrons receives more energy to cross the junction barrier and  move from N type semiconductor to the metal and thus the  current starts to flow. The current is due to the drift of majority charge carriers. Since there is no P type semiconductor there is no holes and thus no minority carriers. When the current starts to flow there is a voltage drop across the terminals, the voltage drop of normal diode is 0.6v to 1.7v, but for schottky diode the voltage drop is 0.15v to 0.45v.

Reverse bias of Schottky diode

 

When the diode is reverse biased the metal is connected to the negative terminal and N type material is connected to the positive terminal. The size of the depletion region increases and the current stops to flow. There is small amount of leakage current. When the applied voltage is increased further the current increases and when increased further the depletion region breaksdown which damages the device permanently.

V-I Characteristics of Schottky diode:

V-I Characteristics of Schottky diode

 

‘I’ is the current generated in the circuit and ‘v’ is the applied external voltage. When compared with PN Junction diode Schottky diode needs very low voltage drop.

Advantages

• It switches very fast, so it is used in high speed switching applications.
• Low junction capacitance
• Operates at high frequencies
• Low cut-in voltage 
• Very low power consumption
• High efficiency

Disadvantages

• It is more expensive
• Operates at low voltages
• It gets heated up very quickly
• It has high reverse current

Application of Schottky diode:

• Diode rectifier
• Voltage clamping application
• High speed switching applications