Aluminum Nitride Substrate (AlN Ceramic)

Aluminium nitride (AlN) is a nitride of aluminium. Its wurtzite phase (w-AlN) is a wide band gap (6.01-6.05 eV at room temperature) semiconductor material, giving it potential application for deep ultraviolet optoelectronics.

AlN was first synthesized in 1877, but it was not until the middle of the 1980s that its potential for application in microelectronics was realized due to its relative high thermal conductivity for an electrical insulating ceramic (70–210 W·m−1·K−1 for polycrystalline material, and as high as 285 W·m−1·K−1 for single crystals).

Aluminium nitride is stable at high temperatures in inert atmospheres and melts at 2800 °C. In a vacuum, AlN decomposes at ~1800 °C. In the air, surface oxidation occurs above 700 °C, and even at room temperature, surface oxide layers of 5-10 nm have been detected. This oxide layer protects the material up to 1370 °C. Above this temperature bulk oxidation occurs. Aluminium nitride is stable in hydrogen and carbon dioxide atmospheres up to 980 °C. 

The material dissolves slowly in mineral acids through grain boundary attack, and in strong alkalies through attack on the aluminium nitride grains. The material hydrolyzes slowly in water. Aluminium nitride is resistant to attack from most molten salts, including chlorides and cryolite.

AlN is synthesized by the carbothermal reduction of aluminium oxide or by direct nitridation of aluminium. The use of sintering aids, such as Y2O3 or CaO, and hot pressing is required to produce a dense technical grade material.