Advancements in Direct Nitridation of Aluminum Method for AlN Crystal Growth

Aluminum nitride (AlN) is a representative wide‐bandgap semiconductor. The main methods used to grow AlN are metal–organic chemical vapor deposition (MOCVD), hydride vapor‐phase epitaxy, physical vapor transport (PVT), and direct nitridation (DN). The MOCVD technique is widely used to grow AlN films, whereas PVT and DN are promising methods for growing AlN bulk crystals. The DN method is environmentally friendly and produces high‐quality AlN crystals at a low cost, which make this method promising for industrial production. However, it is challenging to grow large bulk AlN crystals using DN. Researchers have extensively investigated the influence of the reaction conditions and atmosphere on the growth efficiency and quality of AlN crystals. A growth rate of 18 μm h −1 is achieved by using DN for vapor‐phase growth of AlN crystals. A growth rate of 16–53 μm h −1 and thickness of 67–212 μm were achieved for liquid‐phase growth of AlN crystals. Controlling the temperature control, dopant type, gas composition, and flow velocity is important for enhancing the growth rate and quality of AlN crystals. In this article, recent advances in using DN for AlN growth are reviewed to provide a reference for research on wide‐bandgap semiconductors.