In order to
understand why semiconductors behave as they do, it is necessary
to examine the atomic structure
of elements, and how it affects their electrical properties. The
number of protons and electrons in an atom, and the way in which
they are ordered affects the electrical properties of the element.
Elements in which electrons can move easily are known as conductors;
those which have high resistance to the flow of electrical current
are known as insulators;
and then there is a small group of insulators which can be altered
to become semiconductors.
During the manufacturing process, semiconductors can be transformed
into P-type or N-type
semiconductor by the addition of other elements.