Identification of the deep-level defects in AlN single crystals: EPR and TL studies

X-band electron paramagnetic resonance studies were performed on three different types of AlN single crystals. These studies revealed the presence of two different types of shallow donors, oxygen located in the N site of the AlN lattice and carbon or silicon located in the Al site. These findings are supported by the observation of the light-induced EPR signals with almost similar slightly anisotropic g factors typical for shallow donor in AlN, but strongly different anisotropic EPR line-width ΔB. Distribution of the wave-function density of the unpaired donor electron for both shallow donors is discussed. Moreover, findings related to the deep-donor of the VN centers are presented. The VN center EPR spectra intensity increased drastically after the x-ray irradiation of the sample. The annealing results in recombination thermoluminescence and the deep donor (VN) energy level was estimated to be about 0.75 eV.

Research Highlights
► We study AlN single crystals by X-band electron paramagnetic resonance.
► We show the presence of two different types of shallow donors which seem to show DX behavior.
► We present the discussion of the distribution of the wave function density of the unpaired donor electron.
► Investigations the level depth of the deep-donor nitrogen vacancy using electron paramagnetic resonance and thermoluminescence measurements were performed.