The effect of thermally treated AlN powder on PVT-grown single crystals

Herein, aluminum nitride (AlN) powder is thermally treated via a thermocycle process for use in PVT growth. The thermally treated AlN powder shows reduced impurity concentrations compared to the untreated AlN powder. Two different AlN single crystals are grown by using the untreated and thermally treated powders. The crystallinity, composition, and optical adsorption properties of the as-grown AlN crystals are investigated. The as-grown AlN crystals show two different defect compositions depending on the source powder. The AlN crystal grown from the untreated powder contains a precipitated graphite oxide phase that leads to lattice distortions, while the crystal grown from the heat-treated powder consists of an Al2OC-AlN solid solution with an expanded lattice. These differences in defects lead to slightly different optical adsorption bands, thereby suggesting that the thermocycle process is beneficial for improving the quality of AlN single crystals grown by the PVT method.