Describe the microscopic structure of semiconductor materials. What are the three most commonly used semiconductor materials?

Question

What will be an ideal response?

Answer 1

Analysis:
Semiconductor materials are crystalline with the atoms arranged in a repeated three dimensional array. The distance between atoms in the array is the "lattice constant".
Each atom of a semiconductor has four valence electrons. These electrons participate in covalent bonds with the valance electrons of other atoms.
For certain materials with the properties above, quantum/wave mechanics predicts that the valance electrons may have a total energy [kinetic plus Coulombic potential energy] within certain "allowed" bands. The two most important bands are the valence band containing the valence electrons in covalent bonds and the conduction band containing conduction or free electrons which have obtained enough energy to escape from its covalent bond.
Separating these two allowed bands is the "energy gap" extending over those energies which the electrons are "forbidden" to have.
For semiconductor materials, the energy gap is on the order of 1 electron-Volt [eV].
Silicon is the most common semiconductor material and is used in a variety of applications and devices.
Germanium is used in some optical devices and other special purpose devices.
Gallium Arsenide is a compound III-V semiconductor material. One atom has three and the other has five valence electrons giving an average of four per atom. It is used in microwave, optical, and very high speed digital devices.