P-N JUNCTION DIODE

P-N Junction

• A P-N junction is the line where two types of semiconductor material meet, the p-type and the n-type, inside a semiconductor. This is how the P-N junction is made in a semiconductor: by doping.
• On the positive (p-) side of the semiconductor, there are more holes than electrons.
• On the negative (n-) side, there are more electrons than holes.

Formation of the P-N Junction

• We know that if we use different semiconductor materials to create a P-N junction, there will be a grain limit that stops electrons from moving from one side to the other by bouncing electrons and holes.
• To get around this, we use the doping process. In this case, we'll be able to learn how steroids work. Take a look at a thin piece of p-type silicon material.
• It is possible for a small amount of pentavalent material to change some of the p-type Si into n-type silicon.
• Now, the p-type region, the n-type region, and a connection between them will all be on this sheet.
• There are two types of processes that happen after a P-N link is made: diffusion and drift.
• Different amounts of holes and electrons are present on each side of a joint.
• The electrons move from the n-side to the p-side and the holes move from the p-side to the n-side. Some of these cause a diffuseion current to flow across the joint.
• A donor that is ionized is left behind on the n-side when an electron moves from the n-side to the p-side. This donor is frozen in place.
• An area of positive charge builds up on the n-side of the junction as the process goes on.
• In the same way, when a hole moves from the p-side to the n-side, it leaves behind a charged acceptor on the p-side. This creates a layer of negative charges on the p-side of the junction. It is called the "depletion region" because there is a positive charge in one area and a negative charge in the other.
• Between the two points, there is a positive space charge area. This creates an electric field that flows from the positive charge to the negative charge.
• A charge moves from the p-side to the n-side of the junction because of this electric field.
• The drift is the name for this move. The direction of the drift current is not the same as the direction of the diffusion current.

Biasing Conditions for the P-N Junction Diode

There are two areas where the P-N junction diode can work:

 P-type
N-type

The P-N junction diode can be biased in three different ways, each based on the voltage added:

Zero bias: The P-N junction diode doesn't get any power from the outside.

• For forward bias, the voltage potential's positive terminal is linked to the p-type and its negative terminal is linked to the n-type.
• The negative end of the voltage potential is connected to the p-type, and the positive end is connected to the n-type.

Forward Bias 

IMAGE SOURCE 

• The p-type is forward-biased when it is connected to the positive terminal of the battery and the n-type is forward-biased when it is connected to the negative terminal.
• It is the applied electric field that is going against the built-in electric field at the P-N junction when the junction is forward biased.
• The electric field that is created when you add the two fields together is smaller than the built-in electric field. In the end, this makes the depletion area less resistant and thinner.
• When a high voltage is applied, the resistance in the depletion area is almost nonexistent.
• At a value of 0.6 V, the depletion area in silicon has almost no resistance, so current can flow through it without any problems.

Reverse Bias

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• If you connect the n-type to the positive side of the battery and the p-type to the negative side, the P-N junction is backward biased.
• The applied electric field and the built-in electric field are both going in the same direction.
• The electric field that is created when you add the two fields is in the same direction as the built-in electric field. This makes the depletion area more resistant and thicker.
• If you increase the voltage, the depletion area gets bigger and more resistive.

IMAGE SOURCE (THUMBNAIL)