采用偏振喇曼光谱研究AlN晶体(110)面的各向异性

Study of the Anisotropy in (110) Plane of AlN Crystal by Polarized Raman Spectra

采用平行及垂直配置下的偏振散射装置,对物理气相传输(PVT)法同质籽晶生长的六方AlN晶体进行偏振喇曼研究,测量了激发光偏振方向与光轴成不同角度时各个振动模的偏振喇曼光谱,得到不同振动模式的喇曼信号强度变化。结果表明,对于A1(TO)和E1(TO)振动模,在平行及垂直偏振配置下,其喇曼强度曲线的变化周期均为π/2,相位差均为π/4;对于E■振动模,在平行和垂直偏振配置下,其喇曼强度曲线的变化周期分别为π及π/2。通过喇曼选择定则及实验数据拟合分析得到AlN晶体各个振动模的喇曼张量比,其中,A1(TO)、E1(TO)和E■振动模的喇曼张量比为ZnO的2~3倍。垂直偏振配置下,AlN晶体的喇曼张量比远大于4H-SiC材料,为4~7倍,表明AlN晶体具有更强的各向异性,为纤锌矿结构材料的各向异性研究提供依据。

Using the polarized scattering devices with parallel and vertical configurations,the polarized Raman study of the homogeneously grown hexagonal AlN crystal by the physical vapor transport(PVT)method was carried out.The polarized Raman spectra intensity of each vibration mode were measured when the polarization direction of the excited light was different from the optical axis,and the intensity changes of Raman signals of different vibration modes were obtained.The results show that for A1(TO)and E1(TO)vibration modes,the period of Raman intensity curve isπ/2,and the phase diffe-rence isπ/4 in both parallel and vertical configurations.For E■vibration mode,the period of Raman intensity curve isπin parallel configuration andπ/2 in vertical configuration.According to the Raman selection rules and data fitting,the Raman tensor element ratio for different vibration modes of AlN crystal were obtained.The Raman tensor ratio of A1(TO),E1(TO)and E■vibration mode,is 2 to 3 times that of ZnO.In the vertical polarization configuration,the Raman tensor ratio of AlN is 4 to 7 times that of 4 H-SiC,indicating that AlN has stronger anisotropic properties.The results provide a further understanding of the anisotropy of wurtzite materials.