What is a Semiconductor?

A “semiconductor" is a substance with characteristics intermediate between those of a "conductor" that conducts electricity like metal and an "insulator" through which electricity hardly flows. The ease with which electricity flows is related to the magnitude of the substance’s electrical resistance. If the electrical resistance is high, the current hardly flows, and if the electrical resistance is low, the electric current flows easily.

When electrical conductivity is expressed by resistivity, semiconductors are distributed in the range of 10^-4 to 10⁸ Ωcm, whereas conductors are 10^-8 to 10^-4 Ωcm and insulators are 10⁸ to 10¹⁸ Ωcm.