Electronics Questions: How Semiconductors Work

There is a semiconductor present in all of the computers and stereo equipment, here is a guide to how they work.

Electricity occurs when the electrons of a substance move from atom to atom. Certain materials, called insulators, try to hold on to their electrons, while others, known as conductors, easily give up theirs. But there's another group that doesn't fit neatly into either category: semiconductors.

What Are Semiconductors?

Semiconductors direct or "conduct" the flow of electricity. Silicon is probably the best-known semiconductor because of its wide use in the manufacturing of computers. This inexpensive element can be easily fashioned into digital circuits, and manipulated to increase its conductivity, which is the tendency to conduct electricity. Other common semiconductors include germanium, lead telluride, and gallium arsenate.

As the name implies, semiconductors don't conduct electricity as well as conductors, but they perform much better than insulators. Unfortunately, conductors (i.e., copper, silver, and gold) are unsuitable for many applications. However, semiconductors can be altered by combining them with other substances to help increase conductivity. This procedure is called doping.



The Doping Process

Prior to doping, a semiconductor is pure and referred to as "intrinsic." At this point, it's a fairly poor conductor of electric current because it has electrons that tend to stay put. But during the doping process, an intrinsic semiconductor is treated with a material such as boron, phosphorus, or arsenic that contains atoms that feverishly bond with the atoms in the semiconductor. The movement of electrons in the combined substance is stimulated and conductivity is tremendously improved. The doped semiconductor is now considered "extrinsic" and can be put to use.

Extrinsic Semiconductors: n-type and p-type

Extrinsic semiconductors come in two varieties: n-type and p-type. An n-type semiconductor has a surplus of electrons, and consequently, a negative charge, while a p-type semiconductor has a shortage of electrons, and a positive charge.

What are Diodes?

Diodes are semiconductor devices that have both p- and n-type regions. And the place between these two regions is the p-n junction. Diodes permit electric current to travel along one path, and restrict it from moving along another. When two diodes are joined, they create a transistor.

What are Transistors?

Transistors are probably the most famous semiconductor devices. And while instrumental in the amplification of signals in audio equipment (i.e., radios and headphones), they are also the key ingredient in the development of the computer chip.

Generally, transistors contain three parts: a base (p-type semiconductor), an emitter (n-type), and a collector (n-type). When electricity flows from the emitter to the base, it flows from the emitter to the collector, and when the base-emitter flow is turned off, the emitter-collector flow stops also. The transistor's switching ability makes it ideal for the job of storing information in a computer.

A single computer chip contains thousands of transistors representing unique memory addresses. These addresses constantly receive and discharge data, which is simply coded electric current. Every pattern of data is information, and when a computer is shut down, electricity ceases to flow through the system, and the contents of the addresses are permanently lost. This is basically how temporary memory storage such as random access memory (RAM) operates.

In the world of science, semiconductors are crucial. They are responsible for many of our society's analog and digital advancements, and will continue to play an important role in the future development of computer, laser, and solar energy technologies.

© High Speed Ventures 2011