No current / thermal equilibrium. •PN Junction at equilibrium. 1st Step: diffusion mechanism. 2nd Step: built in Electric Field appears⬄ compensates diffusion. PN Junction. In its basic form a semiconductor diode is formed from a piece of silicon by making one end P type and the other end N type. This means that both ends have different characteristics. One end has an excess of electrons whilst the other has an excess of holes. The energy level sketch above right is a way to visualize the equilibrium condition of the P-N junction. The upward direction in the diagram represents increasing.


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If a diode is forward biased as in Figure above acurrent will increase slightly as voltage is increased from 0 V.

The P-N Junction

In the case pn junction theory a silicon diode a measurable current flows when the voltage approaches 0. As the voltage increases past 0.

Increasing the voltage well beyond 0. The forward voltage, VF, is a characteristic of the semiconductor: The forward current ranges from a few mA for point contact diodes to mA for small signal diodes to tens or thousands of amperes for power diodes.

If pn junction theory diode is reverse biased, only the leakage current of the intrinsic semiconductor flows.

What is Diode? Know PN Junction Theory, Construction & Working of Different Types of Diodes

This is plotted to the left of the origin in Figure above c. This current does pn junction theory increase appreciably with increasing reverse bias until the diode breaks down. At breakdown, the current increases so greatly that the diode will be destroyed unless a high series resistance limits current.

We normally select a pn junction theory with a higher reverse voltage rating than any applied voltage to prevent this. Silicon diodes are typically available with reverse break down ratings of 50,V and higher. It is possible to fabricate diodes with a lower rating of a few volts for use as pn junction theory standards.

This is the leakage that can be explained by theory.

P–n junction - Wikipedia

Thermal energy produces few electron hole pairs, which conduct leakage current until recombination. In actual practice this predictable current is only part of the leakage current.

This charge transfer of electrons and holes across the PN junction is known as diffusion. The width of these P and N layers depends on how heavily pn junction theory side is doped with acceptor density NA, and donor density ND, respectively.

This process continues back and forth until the number of electrons which have crossed the junction have a large enough electrical charge to repel or prevent any more charge carriers from crossing over the pn junction theory.

Since no free charge carriers can rest in a position where there is a potential barrier, the regions on either sides of the junction now become completely depleted of any more free carriers in comparison to the N and P type materials further away from the junction.

The PN junction The total charge on each side of a PN Junction must be equal and opposite to maintain a neutral charge condition around the junction. If the depletion layer region has a distance D, it therefore must therefore penetrate into the silicon by a distance of Dp for pn junction theory positive side, pn junction theory a distance ofDn for the negative side giving a relationship between the two of Dp.

pn junction theory


Under the junction, plots for the charge density, the electric field, and the voltage are reported. The log concentration curves should actually be smoother, like pn junction theory voltage. The space charge region is a zone with a net charge provided by the fixed ions donors or acceptors that have been left uncovered pn junction theory majority carrier diffusion.

When equilibrium is reached, the charge density is approximated by the displayed step function.