Elements (like silicon, germanium, selenium, and others, especially in Group IV of the periodic table) or compounds (like gallium arsenic and indium tellurium), which exhibit electrical properties intermediate between conductive metals and non-conductive or insulating non-metals. Such materials are the basis for modern electronic devices referred to as solid-state devices.
These materials are particularly interesting for their characteristic of allowing current flow in one direction and not in the other, and, so, are used for rectifying (or converting) alternating current (ac) to direct current (dc). See also SELENIUM RECTIFIER, SILICON RECTIFIER, and RECTIFIER WELDER.