Describe the construction and mode of an action of the pn junction semiconductor ?

A pn junction semiconductor is constructed by joining a p-type semiconductor material with an n-type semiconductor material. The p-type material has an excess of positively charged holes, while the n-type material has an excess of negatively charged electrons. When these two materials are brought together, the holes and electrons diffuse across the junction and recombine, creating a depletion region where there are no charge carriers.

The mode of action of a pn junction semiconductor involves the flow of current when a voltage is applied across the junction. When a positive voltage is applied to the p-side and a negative voltage is applied to the n-side, the electric field created across the junction causes the free electrons in the n-type material to move towards the positive side and the holes in the p-type material to move towards the negative side. This movement of charge carriers creates a current flow through the junction.

The pn junction semiconductor can be used in various electronic devices such as diodes, transistors, and solar cells. In a diode, the pn junction allows current to flow in one direction while blocking it in the opposite direction. In a transistor, the pn junction controls the flow of current between the emitter and collector terminals. In a solar cell, the pn junction converts light energy into electrical energy by generating electron-hole pairs when photons are absorbed.