以物理气相传输法自支撑生长氮化铝单晶的表征

Characterization of Freestanding AlN Single Crystals Grown Through a Novel Approach Using the PVT Method

提出了用物理气相传输法自支撑生长氮化铝单晶的新方法,此方法可以在氮化铝烧结体表面一次性获得大量生长的氮化铝单晶。在2373~2523 K的温度条件下经过100 h生长的氮化铝单晶,其最大尺寸为7 mm×8 mm×12 mm,典型直径为5~7 mm。这些原生晶体的表面形貌及结晶质量分别通过扫描电子显微镜、拉曼光谱和高分辨X射线衍射进行表征分析。拉曼光谱E2峰位的半高全宽为5.7 cm^-1,高分辨X射线衍射得到的对称摇摆曲线的半高全宽为93.6弧度秒。经过选择性化学腐蚀后的晶体,其表面的平均腐蚀坑密度为7.5×104cm^-2。逸出气体分析和辉光放电质谱分析结果表明,碳和氧为晶体内部的主要杂质元素,含量分别为28和120μg/g。此方法为高质量氮化铝单晶的获取提供了一个新的途径,这些单晶可以被切成晶片作为后续氮化铝同质外延生长的优良籽晶。使用这些小的籽晶,成功制备出了直径高达60 mm的氮化铝单晶体/晶圆,并具有良好的深紫外光透过性。

A novel approach to grow freestanding AlN single crystals spontaneously using the physical vapor transport(PVT)method was 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.The largest AlN single crystal grown at 2373~2523 K for 100 h is 7 mm×8 mm×12 mm,and the typical diameter is 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 exhibits an E2(high)full width at half maximum(FWHM)of 5.7 cm^-1,whereas the high-resolution X-ray diffraction rocking curve shows a FWHM of 93.6 arc-second for the symmetric reflection.The average etch pit density revealed by preferential chemical etching is 7.5×104 cm^-2,and the major impurities determined by evolved gas analysis and glow discharge mass spectrometry are carbon of 28μg·g^-1 and oxygen of 120μg·g^-1.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 that are up to 60 mm in diameter were successfully prepared.