What causes the depletion region?

In semiconductor physics, the depletion region, also called depletion layer, depletion zone, junction region, space charge region or space charge layer, is an insulating region within a conductive, doped semiconductor material where the mobile charge carriers have been diffused away, or have been forced away by an

How is the pn junction 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 is depletion region formed in 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 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.

What is the ideality factor?

The ideality factor of a diode is a measure of how closely the diode follows the ideal diode equation. The derivation of the simple diode equation uses certain assumption about the cell.

What is the potential barrier in 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.)

What do you mean by depletion?

Depletion is an accounting and tax concept used most often in mining, timber, petroleum, or other similar industries. The depletion deduction allows an owner or operator to account for the reduction of a product’s reserves.

What is the breakdown region of a diode?

For a typical diode, the breakdown mechanism is also called avalanche breakdown. In reverse bias below breakdown voltage, the current is due to generation of carriers (recombination-generation current) in the depletion region and carriers get across the depletion region with the help of the electric field.

What is the breakdown voltage?

The breakdown voltage of an insulator is the minimum voltage that causes a portion of an insulator to become electrically conductive. For diodes, the breakdown voltage is the minimum reverse voltage that makes the diode conduct appreciably in reverse. Some devices (such as TRIACs) also have a forward breakdown voltage.

What is a PN junction?

The PN junction is one of the primary building blocks of semiconductors. Diodes and Thyristors. A diode (one way valve) is a PN junction with p-type on one side and n-type on the other.

What do you mean by reverse bias?

reverse bias The applied d.c. voltage that prevents or greatly reduces current flow in a diode, transistor, etc. For example, a negligible current will flow through a diode when its cathode is made more positive than its anode; the diode is then said to be reverse biased. Compare forward bias. “reverse bias.”

What do you mean by knee voltage?

Knee voltage is also known as “cut-in-voltage”. The minimum amount of voltage required for conducting the diode is known as “knee voltage” or “cut-in-voltage”. And also said as The forward voltage at which the current through PN junction starts increasing rapidly is known as knee voltage.

What is forward biased?

When voltage is applied across a diode in such a way that the diode allows current, the diode is said to be forward-biased. When voltage is applied across a diode in such a way that the diode prohibits current, the diode is said to be reverse-biased.

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.

Is a pn junction a diode?

Reverse Biased PN Junction Diode. When a diode is connected in a Reverse Bias condition, a positive voltage is applied to the N-type material and a negative voltage is applied to the P-type material.

What is the diffusion current?

Diffusion current is a current in a semiconductor caused by the diffusion of charge carriers (holes and/or electrons). The drift current, by contrast, is due to the motion of charge carriers due to the force exerted on them by an electric field.

What is the definition of barrier voltage?

“The barrier voltage is the amount of electromotive force required to start current through the P-N junction. Barrier voltages for silicon typically range from 0.5 – 0.7 volts. Barrier voltages for germanium typically range from 0.2 – 0.3 volts. “

How does a pn junction diode acts as a switch?

A diode conducts (offers 0 resistance ideally i.e., it acts as a short circuit) only when it is forward biased so there will be current flow in the circuit and it offers very high impedance ( it acts as a open circuit) when reverse biased so there will be no current flow. This way p-n junction diode work as a switch.

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.

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 is the threshold voltage?

The threshold voltage, commonly abbreviated as Vth, of a field-effect transistor (FET) is the minimum gate-to-source voltage VGS (th) that is needed to create a conducting path between the source and drain terminals.

What is mobile charge carriers?

Charge carrier. In metals, the charge carriers are electrons. One or two of the valence electrons from each atom is able to move about freely within the crystal structure of the metal. The free electrons are referred to as conduction electrons, and the cloud of free electrons is called a Fermi gas.

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