Junction Diode, Basic Junction diode, Junction breakdown

It conducts an electric current in one direction and blocks it in the other. This behaviour arises from the electrical characteristics of a junction, called a p-n junction. fabricated within a semiconductor crystal. The most commonly used semiconductor material is silicon. The junction diode is useful in a wide variety of applications including the rectification of ac signals (producing dc from ac), the detection of radio signals, the conversion of solar power to electricity, and in the generation and detection of light. It also finds use in a variety of electronic circuits as a switch, as a voltage reference or even as a tunable capacitor. The p-n junction is also the basic building block of a host of other electronic devices, of which the most well-known is the junction transistor. For this reason, a study of the properties and behaviour of the p-n junction is important.


The recombination of free electrons and holes in the vicinity of the junction leaves a narrow region on either side of the junction that contains no mobile charge. This narrow region which has been depleted of mibile charge is called the depletion layer. It extends into both the p-type and n-type regions.Note that the diffusion of holes from the p-type side of the depletion layer leaves behind some uncovered fixed negative charges (the acceptor ions). Similarly, fixed positive charges (donor ions) are uncovered on the n-type side of the depletion layer. There is then a separation of charges: negative fixed charges on the p-type side of the depletion layer and positive fixed charges on the n-type side.

Junction Breakdown

It occurs when the reverse voltage reaches a critical value.