Aluminium arsenide

Aluminium arsenide () is a semiconductor material with almost the same lattice constant as gallium arsenide and aluminium gallium arsenide and wider band gap than gallium arsenide. (AlAs) can form a superlattice with gallium arsenide (GaAs) which results in its semiconductor properties. Because GaAs and AlAs have almost the same lattice constant, the layers have very little induced strain, which allows them to be grown almost arbitrarily thick. This allows for extremely high performance high electron mobility, HEMT transistors, and other quantum well devices. It has the following properties: Thermal expansion coefficient 5 μm/(°C*m) Debye temperature 417 K Microhardness 5.0 GPa (50 g load) Number of atoms in 1 cm3: (4.42-0.17x)·1022 Bulk modulus (7.55+0.26x)·1011 dyn cm−2 Hardness on the Mohs scale: ~ 5 Insolubility in H2O Aluminium arsenide is a III-V compound semiconductor material and is an advantageous material for the manufacture of optoelectronic devices, such as light emitting diodes. Aluminium arsenide can be prepared using well-known methods, such as liquid and vapor-phase epitaxy techniques or melt-growth techniques. However, aluminium arsenide crystals prepared by these methods are generally unstable and generate arsine (AsH3) when exposed to moist air. Little work has been reported on the preparation of aluminium arsenide, mainly because of the practical difficulties involved. Preparation from the melt is difficult because of the high melting point of the compound (about 1,700 °C) and of the extreme reactivity of aluminium at this temperature. A few workers have prepared small crystals from the melt, and polycrystalline ingots have also been produced. The best of this material has an impurity carrier density of the order of 1019/cm3 and is p-type. Aluminium arsenide is a stable compound; however, acid, acid fumes and moisture should be avoided. Hazardous polymerization will not occur. Decomposition of aluminium arsenide produces hazardous arsine gas and arsenic fumes.