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Raman scattering study of compositional homogeneity in InGaN ternary compounds

InGaN 三元化合物成分均匀性的拉曼散射研究

基本信息

批准号：
14550312
负责人：
SUGIURA Touko
金额：
$ 1.86万
依托单位：
Toyota National College of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550312/
关键词：
InGaN Nitride compound Raman scattering immiscibility instability GaN GaMnN Raman spectroscopy phonon

项目摘要

We have studied theoretically and quantitatively the compositional homogeneity of In_xGa_<1-x>N ternary compounds directly grown on sapphire substrates with the aid of low-temperature-grown AIN buffer layer by MOVPE method. First, we found that Ga-N and the In-N bond.length in InGaN kept the bond length of pure GaN and InN from thermo-dynamical analyses even though the In molar fraction x is increasing. Therefore, it suggested that the mixed crystal of InN and GaN did not be homogeneous. Next, we evaluated the macroscopic nature of InxGal-xN by using the SEM image and the TED image, As the results, the whole samples were shown as the thick single crystals. Also, we found the enhancement of the broadening of the PL spectrum as increasing of x. Finally, we analyzed the asymmetric broadening of the E_2 phonon mode of the Raman spectra with the aid of the Spatial Correlation model. That is enhanced in the region of immiscibility suggested theoretically by increasing the indium molar fraction. The correlation length, which corresponds to the decay length of E_2 phonon mode, was estimated. It was on the order of about lOnm, which is on the same order magnitude as the size of the columnar structure suggested by TEM analyses by Kawaguchi et al.[J. Cryst. Growth 189/190 (1998) 24]. It showed a good agreement for applying to the dispersion relation given by Azuhata et al.[Physica B 219/220 (1996) 493]. Furthermore, we tried to analyze the E_<2iow> phonon mode which was strongly reflected the compositional homogeneity of the samples, however, we could not observe. This reason is that the mode has the low density of states and the existence of the eigen-energy around the excited light source.

利用MOVPE方法，从理论上和定量上研究了低温生长AIN缓冲层辅助下直接生长在蓝宝石衬底上的In_xGa_<1-x>N三元化合物的组成均匀性。首先，我们发现了Ga-N和In-N键。尽管in的摩尔分数x增加，但InGaN中的长度保持了纯GaN和InN的键长。因此，这表明InN和GaN的混合晶体不是均匀的。接下来，我们利用SEM图像和TED图像评价了InxGal-xN的宏观性质，结果表明，整个样品显示为厚单晶。最后，利用空间相关模型分析了拉曼光谱中E_2声子模式的不对称展宽。从理论上讲，增加铟的摩尔分数可以增强非混相区。估计了对应于E_2声子模式衰减长度的相关长度。其数量级约为lOnm，与Kawaguchi等人通过TEM分析得出的柱状结构尺寸在同一数量级。结晶的。增长189/190(1998)[24]。它与Azuhata等人给出的色散关系具有很好的一致性[Physica B 219/220(1996) 493]。此外，我们试图分析强烈反映样品成分均匀性的E_< 2low >声子模式，但我们无法观察到。这是因为该模态的态密度低，并且在激发光源周围存在本征能量。