Semiconductor Material

The elements used to produce semiconductors are summarized in Figure below. The oldest elemental semiconductor material is germanium. Though, it is only used to a limited extent today. Silicon based semiconductors account for about 90% of commercial production of all semiconductors. Diamond based semiconductors are a research and development activity with considerable potential at this time. Compound semiconductors not listed include silicon carbide and III-V compounds such as gallium arsenide. III-VI compound semiconductors include: AlN, GaN, InN, AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, InSb, Al_xGa_1-xAs and In_xGa_1-xAs. Columns II and VI of periodic table, not shown in the figure, also form compound semiconductors.

Group IIIA P-type dopants, group IV basic semiconductor materials, and group VI N-type dopants.

The main reason for the inclusion of the IIIA and VIA groups in Figure above is to show the dopants used with the group IVA semiconductors. Group IIIA elements are acceptors, P-type dopants, which accept electrons leaving a hole in the crystal lattice, a positive carrier. Boron is the P-type dopant for diamond , and most the common dopant for silicon semiconductors. Indium is the P-type dopant for germanium.

Group VA elements are donors, N-type dopants, yielding a free electron. Nitrogen and Phosphorus are suitable N-type dopants for diamond. Phosphorus and arsenic are the most commonly used N-type dopants for silicon; though, antimony can be used.

Review

Intrinsic semiconductor materials, pure to 1 part in 10 billion, are poor conductors. N-type semiconductor is doped with a pentavalent impurity to create free electrons. Such a material is conductive. The electron is the majority carrier. P-type semiconductor, doped with a trivalent impurity, has an abundance of free holes. These are positive charge carriers. The P-type material is conductive. The hole is the majority carrier Most semiconductors are based on elements from group IVA of the periodic table, silicon being the most prevalent. Germanium is all but obsolete. Carbon (diamond) is being developed. Compound semiconductors such as silicon carbide (group IVA) and gallium arsenide (group III-V) are widely used.