Applications of semiconductors and p-n junction diode

A p-n junction diode is the basic building block of a large number of semiconductor devices, and a single semiconductor device can in fact contain more than one junction; the electrical properties of such a device can be controlled by controlling the concentration of the dopants used to build it. At this introductory level, it is enough to know the basic role each of the following devices plays; their detailed internal working -- including how a bipolar junction transistor or a rectifier circuit actually operates -- is covered in a later, more advanced treatment.

(1) SOLAR CELL: converts light energy directly into electrical energy; useful for generating electricity in remote areas, and for powering satellites, space probes and space stations. (2) PHOTO RESISTOR: a device whose electrical resistance changes when light falls on it. (3) BI-POLAR JUNCTION TRANSISTOR: a device with two junctions and three terminals, built as either a p-n-p or an n-p-n structure, in which conduction takes place through both holes and electrons together; many other transistor variants exist, tailored to specific requirements, and transistors of some kind are used in almost every semiconductor device. (4) PHOTODIODE: a diode that conducts when illuminated with light. (5) LED (LIGHT EMITTING DIODE): emits light when current is passed through it; household LED lamps use this same underlying technology, and LEDs consume less power, are smaller, last longer, and are more cost-effective than the incandescent lamps they have largely replaced. (6) SOLID-STATE LASER: a special type of LED t …