Time‐Resolved Cathodoluminescence Spectroscopy of Oxygen‐Related Defects in AlN Layers

High‐temperature annealing significantly improves the crystal quality of sputter‐deposited AlN templates, but at the same time introduces a high concentration of oxygen‐related point defects. The origin of this oxygen‐related defect luminescence is studied using time‐resolved and temperature‐dependent cathodoluminescence spectroscopy. Characterization of the defect luminescence reveals a complex multiexponential decay, with a fast component of about 2 ns and slow components of tens to hundreds of nanoseconds. The slow decay is attributed to a donor–acceptor‐pair transition between an O N donor and mainly the ( V Al ‐ O N ) 2− and ( V Al ‐2 O N ) 1− defect complexes as acceptors, whereas the fast component is ascribed to a free electron to acceptor transition involving the same type of acceptors. Furthermore, the impact of these oxygen‐related defects on the quality and transparency of the AlN templates is discussed.