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A p–n junction diode. The circuit symbol is also shown. A p–n junction is a combination of two types of semiconductor materials, p-type and n-type, in a single crystal. The "n" (negative) side contains freely-moving electrons, while the "p" (positive) side contains freely-moving electron holes.
The p–n junction in any direct band gap material emits light when electric current flows through it. This is electroluminescence. Electrons cross from the n-region and recombine with the holes existing in the p-region. Free electrons are in the conduction band of energy levels, while holes are in the valence energy band. Thus the energy level ...
The figure shows a band bending diagram for a p–n diode; that is, the band edges for the conduction band (upper line) and the valence band (lower line) are shown as a function of position on both sides of the junction between the p-type material (left side) and the n-type material (right side). When a p-type and an n-type region of the same ...
In a N-side region near to the junction interface, free electrons in the conduction band are gone due to (1) the diffusion of electrons to the P-side and (2) recombination of electrons to holes that are diffused from the P-side. Holes in a P-side region near to the interface are also gone by a similar reason.
When the n-type and p-type materials are attached together, a momentary flow of electrons occurs from the n to the p side resulting in a third region between the two where no charge carriers are present. This region is called the depletion region because there are no charge carriers (neither electrons nor holes) in it. The diode's terminals are ...
Under a high reverse-bias voltage, the p-n junction's depletion region widens which leads to a high-strength electric field across the junction. [2] Sufficiently strong electric fields enable tunneling of electrons across the depletion region of a semiconductor , leading to numerous free charge carriers .
p–n junction operation in forward bias mode showing reducing depletion width. Both p and n junctions are doped at a 10 15 /cm 3 doping level, leading to built-in potential of ~ 0.59 V. Observe the different quasi-fermi levels for conduction band and valence band in n and p regions (red curves).
Assume that the semiconductor wafer is p-type material.Also assume a ring of n-type material is placed around a transistor, and placed beneath the transistor. If the p-type material within the n-type ring is now connected to the negative terminal of the power supply and the n-type ring is connected to the positive terminal, the 'holes' in the p-type region are pulled away from the p–n ...