Point-Defect Nature of the Ultraviolet Absorption Band in AlN

The authors present an approach for identifying the point defects and defect complexes responsible for the technology-limiting absorption band in the UV-C range (100---280 nm), and the associated luminescence bands, in single-crystalline AlN. The approach employs analysis via density functional theory with the total-charge-balance constraint in the crystal, by incorporating impurity data from secondary-ion mass spectroscopy and power-dependent photoluminescence excitation spectroscopy, to determine the responsible defects and their thermodynamic transition levels. This methodology may help to solve a key problem in AlN-based optoelectronics, and could be extended to other materials.