Optically detected electron paramagnetic resonance of AlN single crystals

Abstract

AlN single crystals have been investigated using photoluminescence ͑PL͒ and optical detection of electron paramagnetic resonance in the PL ͑ODEPR͒. All crystals were found to exhibit intense PL extending from the visible into the near infrared. Several Sϭ1 centers, each with its own distinct emission spectrum, and distant Sϭ1/2 pair recombination centers have been observed via ODEPR. In all except one center, D5, no hyperfine structure was observed preventing chemical identification of the impurity involved. In the case of D5 the partially resolved hyperfine structure suggests interaction with a 100% abundant nucleus of Iϳ5/2. We present arguments to associate it with a displaced host aluminum atom.

Ultraviolet luminescence in AlN

“…In the VIS region, we see a slightly increased luminescence band around 2 eV, while the other transitions are barely affected. This effect has also been described by Mason et al [9] using electron irradiation with energies of 2.5 MeV. However, we shall disregard this band in this paper.…”

Investigation of Oxygen-Related Luminescence Centres in AlN Ceramics

“…Consequently, PSL-EPR yielded the same resonances as RL-EPR. The above described PL-EPR resonances are different from those detected in red and infrared PL of AlN single crystals [20,21] where mainly S = 1 defects were observed.…”

“…EPR data have been discussed as resonances from an oxygen-related defect [14], from Mn 2+ [15], and from an electron trapped on a N vacancy (F centre) [17 to 19]. EPR detected in red and infrared photoluminescence of AlN single crystals [20,21] showed resonances of S = 1=2 and S = 1 systems.…”

EPR and ODMR defect control in AlN bulk crystals

“…The values of the HF structure of this interaction with one 27 Al are A || = 4.0 mT, A ⊥ = 1.9 mT, and perfectly explain the flat -topped line shape of the spectra [6][7][8]. Models proposed for the defect responsible for such interaction are contradictory: (i) displaced Al atom [7] (ii) nitrogen vacancy [6][7][8] or (iii) neutral oxygen substituting for nitrogen [8]. However oxygen could be excluded from this list on the basis of the high-frequency EPR and ENDOR studies [9] where it was shown that oxygen is a shallow donor in AlN that undergoes the DX behavior.…”

“…Such signals of magnetic resonance previously were observed in ODMR, continuous wave (cw) EPR and low frequency ENDOR experiments and were explained as anisotropic hyperfine (HF) interaction of unpaired electron spin with one 27 Al nucleus (I= 5/2, 100% natural abundance). The values of the HF structure of this interaction with one 27 Al are A || = 4.0 mT, A ⊥ = 1.9 mT, and perfectly explain the flat -topped line shape of the spectra [6][7][8]. Models proposed for the defect responsible for such interaction are contradictory: (i) displaced Al atom [7] (ii) nitrogen vacancy [6][7][8] or (iii) neutral oxygen substituting for nitrogen [8].…”