Semiconductor Structure

Overview

  1. Semiconductors are made up of atoms bonded together to form a uniform structure
  2. Each silicon atom has four valence electrons which are shared, forming a covalent bonds with the four surrounding Si atoms.
  3. Understanding how these atoms are arranged is vital in understanding the material properties of different semiconductors, and how best to engineer them.

Semiconductors, such as Silicon (Si) are made up of individual atoms bonded together in a regular, periodic structure to form an arrangement whereby each atom is surrounded by 8 electrons. An individual atom consists of a nucleus made up of a core of protons (positively charged particles) and neutrons (particles having no charge) surrounded by electrons. The number of electrons and protons is equal, such that the atom is overall electrically neutral. The electrons surrounding each atom in a semiconductor are part of a covalent bond. A covalent bond consists of two atoms "sharing" a single electron. Each atom forms 4 covalent bonds with the 4 surrounding atoms. Therefore, between each atom and its 4 surrounding atoms, 8 electrons are being shared. The structure of a semiconductor is shown in the figure below.

Schematic representation of covalent bonds in a silicon crystal lattice. Each line connecting the atoms represents an electron being shared between the two. Two electrons being shared are what form the covalent bond.