What Is The Crystal Structure Of Aluminium Arsenide?

Aluminium arsenide (AlAs) has a zincblende crystal structure, which is a type of cubic crystal lattice. In the zincblende structure, each atom is surrounded by four nearest neighbors in a tetrahedral arrangement, with alternating atoms of aluminium and arsenic occupying the corners of the tetrahedra.

The unit cell of AlAs consists of two interpenetrating face-centered cubic lattices, where one sub-lattice contains aluminium atoms and the other contains arsenic atoms. The lattice constant of AlAs is 5.66 Å, which is smaller than that of gallium arsenide (GaAs), another common III-V compound semiconductor that has a similar crystal structure.

Within the crystal lattice, covalent bonding occurs between the aluminium and arsenic atoms, creating a stable structure. This covalent bonding is due to the electronegativity difference between aluminium and arsenic, where the arsenic atoms have a higher electronegativity and attract electrons towards themselves, forming covalent bonds with the aluminium atoms.

Furthermore, AlAs is a direct bandgap semiconductor with a bandgap energy of approximately 2.16 eV at room temperature. This property makes it useful for applications in optoelectronics, such as light-emitting diodes (LEDs), solar cells, and laser diodes.