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The 14 mm x 12 mm AlN single crystal is synthesized by the homoepitaxial physical vapor transport method. The crystal sample sliced from the boule is processed by lapping and chemical mechanical processes (CMP). The sample is characterized by Raman spectrometer, high resolution X-ray diffractometer, X-ray photoelectron spectrometer and photoluminescence spectrometer. The Raman results show that the full width at half maximum (FWHM) of the E2 (high) phonon mode of Raman spectrum is 3.3 cm-1 in the central region of the sample, and the FWHM of the E2 (high) phonon mode of Raman spectrum is 4. 3 cm-1 in the edge of the sample, the AlN single crystal exhibits high crystal quality. The FWHM of the X-ray rocking curve increase to 100" in the central region of the homoepitaxial growth crystal, while the FWHM of the X-ray rocking curve is 205" in the edge region of the homoepitaxial growth crystal, which indicates defects exist in the crystal. XPS results show that there are C, O, Si impurity elements in the crystal, and the atomic concentration of the impurities is 0.74%, 1.43% and 2.14%, respectively. It is found that the mainly oxygen impurities exist in the crystal in the form of Al--O, N--Al--O bonding. PL spectra show that crystal contains VAl-ON compound defect and VAl point defect. [ABSTRACT FROM AUTHOR]