AlAs

Aluminum arsenide (AlAs) is a binary III–V semiconductor compound with the zinc blende crystal structure. It is commonly grown as a crystalline solid and is widely used in combination with gallium arsenide (GaAs) to form AlGaAs alloys, enabling precise band-gap engineering for optoelectronic and high-speed electronic devices. The lattice constant is about 5.66 angstroms, closely matching GaAs, which facilitates high-quality lattice-m matched heterojunctions.

Electronic structure: AlAs has an indirect band gap at room temperature, with the conduction-band minimum located at the X point of the Brillouin zone and the valence-band maximum at Γ. The indirect gap is about 2.16 eV, while the direct gap at Γ is larger, typically around 3.0 to 3.2 eV. These properties make pure AlAs less favorable for light emission than GaAs, but alloys with GaAs extend the usable wavelength range and device functionality.

Growth and materials integration: AlAs is typically grown by molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD). It forms a continuous solid solution with GaAs (AlxGa1−xAs) across the full composition range, enabling lattice-matched quantum wells, barriers, and other heterostructures used in various electronic and optoelectronic devices.

Applications and safety: AlAs and its alloys are used in high-speed electronics, quantum wells, and optoelectronic devices that operate across near-UV to visible wavelengths when alloyed. Because arsenic compounds are toxic, handling requires appropriate safety protocols and disposal.