Electron paramagnetic resonance of a donor in aluminum nitride crystals

Abstract

Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectra are obtained from a donor in aluminum nitride (AlN) crystals. Although observed in as-grown crystals, exposure to x rays significantly increases the concentration of this center. ENDOR identifies a strong hyperfine interaction with one aluminum neighbor along the c axis and weaker equivalent hyperfine interactions with three additional aluminum neighbors in the basal plane. These aluminum interactions indicate that the responsible center is a deep donor at a nitrogen site. The observed paramagnetic defect is either a neutral oxygen substituting for nitrogen (ON0) or a neutral nitrogen vacancy (VN0).

Silicon in AlN: shallow donor and DX behaviors

“…1 shows EPR spectra in undoped and unintentionally Si-doped AlN samples measured in darkness at room temperature for the magnetic field parallel to the c-axis (B||c). In nominal undoped AlN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 samples, the EPR spectrum of the neutral N vacancy ( 0 N V ) [13] was observed (Fig. 1a), whereas in unintentionally Sidoped samples, only a sharp line was detected (Fig.…”

Defects at nitrogen site in electron-irradiated AlN

“…7 In a more recent study of as-grown AlN, an EPR spectrum with an unresolved hf structure due to the interaction with 27 Al nuclei ͑nuclear spin I = 5 / 2 and 100% natural abundance͒ was observed and assigned to either the neutral N vacancy ͑V N 0 ͒ or the shallow O N donor. 8 In this letter, we report our observation of an EPR spectrum with an electron spin S = 1 / 2 and a clear hf structure in AlN after electron irradiation. The structure is shown to be due to the hf interaction between the electron spin and the nuclear spins of four 27 Al nuclei.…”

“…With the effective electron spin S = 1 / 2, the charge state of the N vacancy is expected to be neutral. However, V N 0 has already been suggested as a possible model for another EPR center with C 3v symmetry by Evans et al 8 We modeled V N in a 432-atom hexagonal AlN supercell using a ⌫-point sampling of the Brillouin zone. This model worked very well for other defects in AlN.…”

EPR and ODMR defect control in AlN bulk crystals

“…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].…”