What is a Semiconductor?

A "semiconductor" is a material with intermediate properties between a "conductor" that conducts electricity well, like metals, and an "insulator" that barely conducts electricity. Two types of semiconductors, N-type and P-type, can be created by adding impurities (diffusion/doping) to an intrinsic semiconductor that does not contain impurities. These will exhibit the properties of a conductor or insulator when voltage, current, light, heat, etc., are applied. Furthermore, by combining these, devices such as diodes, transistors, and ICs (integrated circuits) can be created.

The ease with which electricity flows is related to the magnitude of the material's electrical resistance. If the electrical resistance is high, the current will not flow easily, and if the electrical resistance is low, the current will flow easily. When the ease with which electricity passes is expressed as resistivity, conductors are: 10^-8 to 10^-4Ωcm, insulators are: 10⁸ to 10¹⁸Ωcm, while semiconductors are in the range of around 10^-4 to 10⁸Ωcm. Conductors include gold, silver, copper, iron, and aluminum. Insulators include glass, rubber, oil, and plastic. Semiconductors include single elements such as silicon (Si) and germanium (Ge), and compounds such as gallium arsenide (GaAs), silicon carbide (SiC), silicon germanium (SiGe), and gallium nitride (GaN).