1. Photos of AlN crystal sample(a) Bulk AlN crystal; (b) Polished AlN crystal

2. Schematic view of high temperature annealing process(a) High temperature annealing furnace; (b) High temperature annealing process

3. EBSD of AlN crystal sample(a) EBSD Kikuchi patterns of AlN crystal without annealing; (b) Band slop obtained from EBSD mapping date; (c) Pole figures of AlN without annealing

4. XRD ω-scan rocking curves of AlN (10¯12) diffractions

5. Raman spectra of AlN samples without and with annealing at different temperatures

6. Optical absorption spectra of the AlN crystals with and without annealing(a) Absorption spectra of the AlN without and with annealing at different temperatures with right enlarged spectra showing an absorption peak at 634 nm; (b) Correlation curves of (αE)² on E with inset showing the band gap of AlN without and with annealing at different temperatures

7. SIMS depth profiles of AlN crystal without (a) and with annealing at 1600 ℃ (b)