Semiconductors

Semiconductors are some of the most important components in electronics. In general, semiconductors are a solid whose electrical conductivity is in between that of a metal and that of an insulator. Because of their unique makeup, they can be controlled over a wide range, either permanently or dynamically.

In the field of electronics, semiconductors are tremendously important both technologically and economically. Silicon is the most commercially used semiconductor, though dozens of other materials can be used as well.

Semiconductors are very similar to insulators but there are important differences between the two. The two categories of differ primarily in that insulators have larger band gaps, which makes it very difficult for electrons to pass through, while semiconductors have smaller band gaps that allow for many other means to control their electrical properties.

Manufacturers can modify semiconductors by introducing impurities into them. The process is known as doping. A way of thinking of this is to assume that one atom of impurity creates one hole for electron passage. In fact, with the addition of a sufficiently large proportion of dopants, semiconductors can conduct electricity nearly as well as metals.

Semiconductors are usually classified as either N-type or P-type. It is important for the novice to learn the principles behind these classifications and how they work. The junctions between regions of N- and P-type semiconductors have built-in electric fields, which cause electrons to escape, and are critical to semiconductor device operation.

In addition to permanent modification through doping, the electrical properties of semiconductors are often dynamically modified by applying electric charges or fields. It is through this ability to control conductivity in small and well-defined regions of the semiconductor material that has led to the development of a broad range of semiconductor devices, like transistors.

Semiconductor devices with dynamically controlled conductivity are the building blocks of integrated circuits, like the microprocessor. These "active" semiconductors are combined with simpler passive components, such as semiconductor capacitors and resistors, to produce a variety of electronic devices.

It can be argued that without semiconductors many of today's modern devices would not be possible. A working knowledge of semiconductors is a prerequisite to a working knowledge of electronics. You can find a lot of good information on this topic either online or in electronics textbooks. The time spent learning in this area will pay off big later on when more advanced techniques are studied.