What causes the depletion region?

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.

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.

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.

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.)

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.

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.

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.

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.

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.”

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.

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.

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.

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.

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.

“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. “

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.

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.

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.

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.

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.