In semiconductor crystals, the atomic arrangement is defined by a combination of a Bravais lattice and a basis.

The Bravais lattice provides the geometric framework—an infinite array of points arranged with translational symmetry—where each point has an identical environment.

There are 14 unique Bravais lattices in three dimensions, grouped into seven crystal systems such as cubic, tetragonal, and orthorhombic. Mathematically, any point in a Bravais lattice can be described using integer multiples of three primitive vectors.

The basis, on the other hand, specifies the set of atoms attached to each lattice point, determining the chemical identity and spatial arrangement of atoms within the unit cell.

Together, the Bravais lattice and basis form the complete crystal structure. For example, silicon and germanium have a diamond cubic structure, which consists of a face-centered cubic (FCC) Bravais lattice with a two-atom basis.

Gallium arsenide (GaAs) has a zinc blende structure, also based on an FCC lattice but with a two-atom basis of different elements.

This combined structure influences key semiconductor properties such as electronic band structure, carrier mobility, and defect behavior, and plays a critical role in fabrication techniques like epitaxial growth.