What is the PN junction theory?

PN Junction Theory. As a result, the charge density of the P-type along the junction is filled with negatively charged acceptor ions ( NA ), and the charge density of the N-type along the junction becomes positive. This charge transfer of electrons and holes across the PN junction is known as diffusion.

What is PN junction and how it is formed?

Formation of a P-n junction. P-n junctions are formed by joining n-type and p-type semiconductor materials, as shown below. Since the n-type region has a high electron concentration and the p-type a high hole concentration, electrons diffuse from the n-type side to the p-type side.

How does a pn junction diode work?

To understand how a pn-junction diode works, begin by imagining two separate bits of semiconductor, one n-type, the other p-type. As a result, the free electrons and holes near the junction tend to eat each other, producing a region depleted of any moving charges. This creates what is called the depletion zone.

What is a potential barrier of a pn junction?

As more electrons and holes flow in the depletion region the number of positive and negative ions is reduced, causing the depletion region to narrow. The energy loss in overcoming the barrier potential results in a voltage drop across the PN junction equal to the barrier potential. ( 0.7V for Si, 0.3V for Ge.)

How a pn junction diode is formed?

P-n junctions are formed by joining n-type and p-type semiconductor materials, as shown below. Since the n-type region has a high electron concentration and the p-type a high hole concentration, electrons diffuse from the n-type side to the p-type side.

What is the cut in voltage?

There is a definite forward voltage at which the diode starts to conduct significantly. This is called the knee voltage or cut-in voltage and is equal to the barrier potential of the p-n junction.

What do you mean by avalanche breakdown?

Avalanche breakdown is a phenomenon that occur in both insulating and semiconducting materials. It is a form of electric current multiplication that can allow very large currents within materials which are otherwise good insulators. It is a type of electron avalanche.

What is donor impurities?

Doped semiconductors: donor impurities. A silicon lattice with a single impurity atom (Phosphorus, P) added. As compared to Si, the Phosphorus has one extra valence electron which, after all bonds are made, has very weak bonding.

What is meant by zero bias?

In a semiconductor P-N junction, forward bias occurs when the P-type material is positive with respect to the N-type material; in reverse bias, the P-type material is negative with respect to the N-type material. When two electrodes are at the same potential, they are said to be at zero bias.

What is meant by a potential barrier?

The potential barrier in the pn junction is the barrier which does not allow charge flow across the junction normally. Normally in a pn junction the value of barrier potential is typically 0.3-0.7V. Depending upon the material used.

What is the definition of a pn junction diode?

A diode (one way valve) is a PN junction with p-type on one side and n-type on the other. When a positive voltage is applied to the p-type side (forward bias), it shrinks and overcomes the depletion zone, causing the current to flow from the p-type to the n-type side.

What is the PNP junction?

PNP Transistor is a two-junction (bipolar) semiconductor transistor with a P-type collector and emitter, and an N-type base. In such a device, the current amplification arises from the injection of holes from the emitter into the base, and their subsequent collection in the collector.

How is pn junction formed in semiconductor diode?

Formation of a P-n junction. P-n junctions are formed by joining n-type and p-type semiconductor materials, as shown below. Since the n-type region has a high electron concentration and the p-type a high hole concentration, electrons diffuse from the n-type side to the p-type side.

What is the cause of Zener breakdown?

It occurs in a reverse biased p-n diode when the electric field enables tunneling of electrons from the valence to the conduction band of a semiconductor, leading to a large number of free minority carriers which suddenly increase the reverse current. The I-V curve for a diode showing avalanche and Zener breakdown.

How is the depletion layer formed in a pn junction?

Depletion Region. When a p-n junction is formed, some of the free electrons in the n-region diffuse across the junction and combine with holes to form negative ions. In so doing they leave behind positive ions at the donor impurity sites.

What is a PN junction diode?

junction diode (plural junction diodes) (physics) A semiconductor rectifying device in which the barrier between the two regions of opposite conductivity (n-type and p-type) type produces the rectification. All solar cells are junction diodes.

How is a P type semiconductor formed?

Pentavalent impurities Impurity atoms with 5 valence electrons produce n-type semiconductors by contributing extra electrons. Trivalent impurities Impurity atoms with 3 valence electrons produce p-type semiconductors by producing a “hole” or electron deficiency.

What is the meaning of breakdown voltage?

For diodes, the breakdown voltage is the minimum reverse voltage that makes the diode conduct in reverse. The breakdown voltage of an insulator is the minimum voltage that causes a portion of an insulator to become electrically conductive.

What is meant by semiconductor diode?

A diode made of semiconductor components, usually silicon. The cathode, which is negatively charged and has an excess of electrons, is placed adjacent to the anode, which has an inherently positive charge, carrying an excess of holes. At this junction a depletion region forms, with neither holes nor electrons.

When a pn junction is forward biased?

Forward Biased PN Junction Diode. When a diode is connected in a Forward Bias condition, a negative voltage is applied to the N-type material and a positive voltage is applied to the P-type material. If this external voltage becomes greater than the value of the potential barrier, approx.

What is meant by p type and n type semiconductor?

In p-type semiconductors, holes are the majority carriers and electrons are the minority carriers. P-type semiconductors are created by doping an intrinsic semiconductor with acceptor impurities. A common p-type dopant for silicon is boron or gallium.

Leave a Comment