Essential Guide to Computer Data Storage: From Floppy to DVD, The

Basics of Semiconductor Memory Technology

Semiconductors

Silicon and germanium are two basic materials for semiconductor devices. When found in their pure crystalline form, they have a diamond-cubic, perfectly regular lattice with four valence electrons per atom. These electrons interact with other electrons within the lattice and are not free to move, turning these materials into insulators. But, when implanted with a small amount of certain impurities, both germanium and silicon can conduct electricity.

The impurities are of two basic types: donors and acceptors. The donors, created by implanting antimony, arsenic, phosphorus, and so on, contribute excess electrons to the crystal, while the acceptors (gallium, indium, etc.) create electron ...