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王智昊,吴亮.以物理气相传输法自支撑生长氮化铝单晶的表征[J].稀有金属材料与工程(英文),2020,49(10):3337~3352.[wzh and wuliang.Characterization of Freestanding AlN Single Crystals Growth through a Novel Approach Using the PVT Method[J].Rare Metal Materials and Engineering,2020,49(10):3337~3352.]
Characterization of Freestanding AlN Single Crystals Growth through a Novel Approach Using the PVT Method
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Received:August 28, 2019  Revised:November 11, 2019
Key words: AlN substrates  physical vapor transport  surface morphology  structural quality
Foundation item:国家自然科学基金项目(面上项目,重点项目,重大项目)
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wzh and wuliang  
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      In this paper, a novel approach to grow freestanding AlN single crystals spontaneously using the physical vapor transport method is presented. Dozens of single crystals can be obtained on the surface of a pre-sintered AlN powder source in a single growth run using this approach. In this study, the largest AlN single crystal for 100 h of growth at 2373–2523 K was 7 × 8 × 12 mm3, and the typical diameter was 5–7 mm. The surface morphologies of the as-grown crystals were investigated by scanning electron microscopy, whereas the structural quality of the crystals was characterized by Raman spectroscopy and high-resolution X-ray diffraction. Raman spectroscopy exhibited an E2 (high) full width at half maximum (FWHM) of 5.7 cm-1, whereas the high-resolution X-ray diffraction rocking curve showed a FWHM of 93.6 arcsec for the symmetric reflection. The average etch pit density revealed by preferential chemical etching was 7.5 × 104 cm-2, and the major impurities determined by evolved gas analysis and glow discharge mass spectrometry were carbon at 28 ppmw and oxygen at 120 ppmw. The proposed novel approach provides a new means of obtaining high-quality AlN single crystals, which can be cut into wafers and are ideal as seeds for subsequent homoepitaxial AlN growth. Using these small seeds, crack-free bulk AlN single crystal/wafers that have excellent deep UV transparency and are up to 60 mm in diameter were successfully prepared for the first time.