Lattice constant

Lattice constant, or a, defines the distance between atoms in crystal lattice. It is a measure of structural compatibility between different materials.

Lattice constants are measured in nanometers, and may differ for different axes in the crystal structure for non-cubic crystals.

Lattice constant matching is important for growth of thin layers of materials on other materials; when the constants differ, strains are introduced into the layer, which prevents epitaxial growth of thicker layers without defects.

Matching of lattice structures between two different semiconductor materials allows forming of a region of band gap change in the material without introducing a change in crystal structure. It allows costruction of advanced light emitting diodes and diode lasers.

For example, gallium arsenide and aluminium arsenide have almost identical lattice constant, making it possible to grow almost arbitrarily thick layers of one on the other one.