Effect of High-Temperature Annealing on Optical Properties of AlN Crystals

doi:10.16553/j.cnki.issn1000-985x.2026.0042

Abstract

Abstract: In this paper，AlN single crystals were grown by physical vapor transport method and subjected to high-temperature annealing treatment. By adjusting the high-temperature annealing time，temperature and other parameters，AlN single crystals with high transmission performance in the deep-ultraviolet band were successfully obtained. The surface morphology，crystalline quality and optical properties were systematically characterized. The results indicate that high-temperature annealing process effectively reduces the defect density and significantly improves the crystalline quality of AlN crystals. Specifically，the full width at half maximum of （0002） plane rocking curve decreases from 91.2″ to 28.5″. However，high annealing temperature （1 900 ℃） leads thermal corrosion morphology on the wafer surface and there is no transmittance in the deep-ultraviolet and visible light regions. The high-temperature annealing process has no significant effect on the optical properties of the central colorless region of the AlN wafer，and significantly improves the optical transmission performance of the colored edge region. Compared with AlN wafers before annealing，the most significant effect on the improvement of optical properties is achieved under annealing process at 1 800 ℃ for 7 h. The transmittance at 265 nm increases from 23.59% to 48.61%，and the corresponding absorption coefficient decreases from 45.26 cm^-1 to 22.59 cm^-1. The research provides theoretical guidance for improving the performance of AlN-based optoelectronic devices.

Key words: high-temperature annealing; AlN single crystal; point defect; optical absorption; ultraviolet transmittance

CLC Number:

TN304.2

ZHANG Ying, XU Zongwei, WANG Zenghua, CHENG Hongjuan. Effect of High-Temperature Annealing on Optical Properties of AlN Crystals[J]. Journal of Synthetic Crystals, 2026, 55(6): 867-877.

Figures/Tables 10

Fig.1 Process curves of AlN wafers under different high-temperature annealing conditions. （a） Different annealing time；（b） different annealing temperatures

Fig.2 Photographs of AlN wafers before annealing and after isothermal annealing treatments at 1 800 ℃ for 3，5 and 7 h

Fig.3 Photographs of AlN wafers before annealing and after isothermal annealing treatments at 1 700，1 800 and 1 900 ℃ for 7 h

Fig.4 FWHM of （0002） plane rocking curves for AlN wafers before and after annealing treatment

Fig.5 Micrographs of AlN wafers for different annealing time. （a） SEM images；（b） AFM images

Fig.6 Micrographs of AlN wafers at different annealing temperatures. （a） SEM images；（b） AFM images

Fig.7 Optical spectra of central colorless region for different annealing time. （a），（b） UV-Vis transmission spectra and transmittance evolution；（c），（d） UV-Vis absorption spectra and absorption coefficient evolution；（e），（f）（αhν）2-hν curves and band gap evolution

Fig.8 Optical spectra of edge colored region for different annealing time. （a），（b） UV-Vis transmission spectra and transmittance evolution；（c），（d） UV-Vis absorption spectra and absorption coefficient evolution；（e），（f）（αhν）2-hν curves and band gap evolution

Fig.9 Optical spectra of central colorless region at different annealing temperatures. （a），（b） UV-Vis transmission spectra and transmittance evolution；（c），（d） UV-Vis absorption spectra and absorption coefficient evolution；（e），（f）（αhν）2-hν curves and band gap evolution

Fig.10 Optical spectra of edge colored region at different annealing temperatures. （a），（b） UV-Vis transmission spectra and transmittance evolution；（c），（d） UV-Vis absorption spectra and absorption coefficient evolution；（e），（f）（αhν）2-hν curves and band gap evolution

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