Schottky Diode Tutorial - Structure, Characteristics, Advantages
Schottky Diode - An Introduction:
We know that based of reverse recovery characteristics, the Power diode is classified as
Slow recovery diode (Line-frequency diodes)
Fast recovery diode (High-frequency diodes)
SiC-based Schottky diodes
In this post, let us discuss the schotttky diode is detail. It is recommended to read about the Power Diode Classification and The Difference between Schottky diode and PN junction diode...
Schottky Diode Basics:
- Schottky diode is named for its discoverer Walter Schottky.
- A Schottky diode consists of a Metal - Semiconductor junction not Semiconductor - Semiconductor junction as that of normal P-N junction Diode.
- Here the semiconductor (N-type) will be normally silicon.
- The metal will be typically
gold, silver, aluminium, nickel, chromium, platinum, tungsten, or alloys of exotic metals.
Schottky Diode Structure:
- A forward biased Schottky diode has the Current-Voltage characteristic similar to that of bipolar junction diode.
As the diode conducts using majority carriers, it has lower forward voltage drop (typically 0.35V) than the silicon diode(typically 0.6V).
- It is a unipolar device (current conduction will happen due to majority carrier only).
- Schottky diodes have lower on-state losses than pn-junction diodes but also have low maximum reverse voltage rating (typically 50V to 200V).
Why Schottky diode is suitable for SMPS / Switching circuits?
Why Schottky diode switching faster than bipolar Junction Diode?
- In this diode, the electrons are the majority carriers on both sides of the junction (ie, in the N-type semiconductor as well as in the metal).
- So depletion layer is not formed near the junction. (Ie no stored charge carriers in the junction)
- This scenario will give the following benefits:
With reverse bias condition, there is no significant current from the metal to the semiconductor.
Thus the time delay existing in the junction diodes due to hole - electron recombination is absent in schottky diode.
- Hence, the schottky diode can switch OFF faster than a bipolar diode.
Hot carrier diode:
- When it is forward biased, conduction electrons on the N side gains sufficient energy to cross the junction and enter the metal.
- Since these electrons plunge into the metal with large energy, they are commonly called as hot carriers.
- Hence it is also called as hot carrier diode.
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