Working principle of Schottky diode

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Schottky diodes, in essence, are when metal and semiconductor materials are in contact, and the energy band at the interface semiconductor is bent, forming a Schottky barrier.

This definition is relatively official, and it is estimated that you will forget it at a glance.

So how to understand it in a popular way?

In fact, when metal and semiconductor are in contact, electrons will run from the semiconductor to the metal. When the semiconductor loses electrons, it will be positively charged to form a space charge region (composed of immovable positive ions). This space charge region will prevent the electrons of the semiconductor from continuing to move to the metal, that is to say, a Schottky barrier is formed.

When a forward voltage (metal voltage>semiconductor voltage) is applied to this potential barrier, the potential barrier between the semiconductor and the metal is reduced. In this way, electrons will flow from the semiconductor to the metal, forming a forward current.

On the contrary, when the reverse voltage is applied, the potential barrier is increased, and the current is basically 0, that is to say, the reverse bias is cut off.

This is how Schottky diodes work.

It is estimated that there will be doubts: Doesn’t the diffusion diffuse from the direction of high concentration to low concentration? How can metal lose electrons? There are so many free electrons in metals, is it wrong?

Of course it is right to be wrong, and it cannot be explained by diffusion at this time.

How to explain it?

Let’s understand it this way. There are many free electrons in a metal block. We call them “free”, which means that they can move freely in the metal block. Only a little voltage is applied, and the electrons can move in the metal block.

But if you want them to break away from the metal and fly into the vacuum, this should be quite difficult. Difficult to return, there is a parameter to measure how difficult it is, and that is the work function.

Work function is also called work function, which is the minimum energy required to get electrons from the inside of a solid to the outside.

Facts show that this energy is greater for metals than for semiconductors (semiconductors are called electron affinity). So, it's harder for electrons to get out of metals, and it's a little easier for semiconductors.

Therefore, when metals and semiconductors are brought together, it is the metals that get electrons.

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