AlN

Aluminum nitride (AlN) is an inorganic compound that crystallizes in a hexagonal wurtzite structure. It is a wide-bandgap semiconductor with a bandgap around 6.0 to 6.2 eV, which contributes to high electrical resistivity and low intrinsic charge carriers, enabling stable operation at elevated temperatures.

AlN exhibits very high thermal conductivity for a ceramic, typically about 140–180 W/m·K at room temperature, making it an effective heat spreader and thermal management material. It also has a high melting point and good chemical stability, with a dielectric constant around 8–9 and a high dielectric breakdown strength. The wurtzite structure gives rise to piezoelectric properties, which are useful in certain signal-processing and sensing applications.

Production and processing of AlN involve multiple routes. Dense ceramics are produced by sintering or hot pressing in nitrogen environments with sintering aids (for example, yttria) to promote densification while limiting oxidation. Powder routes include carbothermal reduction and nitridation of aluminum sources. Thin films and single crystals are grown by epitaxial techniques such as metal-organic chemical vapor deposition (MOCVD) or hydride vapor phase epitaxy (HVPE).

Applications include use as substrates for GaN-based electronics and optoelectronics, especially high-electron-mobility and UV devices, due to lattice considerations and thermal properties. AlN is also employed in high-temperature electronics, electrical insulation for power devices, packaging, and some surface acoustic wave (SAW) devices. While offering excellent thermal and dielectric performance, its processing can be challenging and cost-intensive compared with some other ceramics.