Semiconductor - Materials

Materials

Certain pure elements found in Group IV of the periodic table are semiconductors. The most commercially important of these elements are silicon and germanium. Binary compound between elements in Groups III and V, or Groups II and VI, or groups IV and VI also form semiconductors, as do certain ternary compounds and alloys.

Dozens of other materials are used, including germanium, gallium arsenide, and silicon carbide. A pure semiconductor is often called an “intrinsic” semiconductor. The electronic properties and the conductivity of a semiconductor can be changed in a controlled manner by adding very small quantities of other elements, called “dopants”, to the intrinsic material. This is typically achieved in crystalline silicon by adding impurities of boron or phosphorus to the melt and then allowing it to solidify into the crystal. This process is called "doping" and the semiconductor is termed "extrinsic".

Common semiconducting materials are crystalline solids, but amorphous and liquid semiconductors are also known. These include hydrogenated amorphous silicon and mixtures of arsenic, selenium and tellurium in a variety of proportions. Such compounds share with better known semiconductors intermediate conductivity and a rapid variation of conductivity with temperature, as well as occasional negative resistance. Such disordered materials lack the rigid crystalline structure of conventional semiconductors such as silicon and are generally used in thin film structures, which do not require material of higher electronic quality, being relatively insensitive to impurities and radiation damage. Organic semiconductors, that is, organic materials with properties resembling conventional semiconductors, are also known.