【作者】 肖祁陵；

【导师】 张萌；

【作者基本信息】 南昌大学 ， 材料学， 2006， 硕士

【摘要】 近年来，尽管GaN基光电子材料和器件得到迅猛发展，但对材料本身的研究还很不充分，GaN基材料生长和性能研究方面还需做大量工作，仍存在一些影响产业化的问题急需解决。目前氮化镓材料中位错的研究吸引了众多学者的极大关注。国内外许多研究小组利用透射电子显微术和X射线衍射对GaN薄膜位错的研究集中在用不同的测试方法对位错密度的分析，但通过这些方法表征的位错密度与器件发光性能存在矛盾。 鉴于此，本论文在系统总结了常用于研究和表征薄膜的方法的优缺点的基础上，利用高分辨X射线衍射技术对常压MOCVD制备的GaN／Al₂O₃薄膜进行了常规晶体结构的表征，对外延层的相组成、真实衍射峰的位置、准确晶格参数、外延层和衬底晶轴取向关系、外延片在应力作用下的弯曲半径及应力大小进行了讨论；并利用倾斜对称法和掠入射、掠出射分析技术考察了样品的半高宽和位错密度，结合样品的发光性能，进一步了解位错密度与发光性能的关系。在这些系统、细致的实验基础上，总结出了与样品发光性能一致的表征位错密度的掠入射方法。这种表征方法的明确，不仅有利于进一步了解薄膜的位错密度的分布，对实际生产也有指导意义。论文的主要内容与结论如下： 1、采用直射模式所得样品衍射图谱中只出现GaN（00.2）和（00.4）晶面的最强特征衍射峰，表明所研究的GaN薄膜都为纤锌矿六方结构，沿c轴择优取向，且薄膜与衬底之间在（00.1）方向上并未形成很好的取向关系，存在着取向偏差。消除仪器零点误差，对测量数据进行修正得到的六个样品的c轴晶格常数与标准值c=0.5185nm比较，相差甚小，且都稍大于标准值，表明样品皆受压应变。 2、采用高分辨X射线高强衍射模式，以衬底衍射峰为参考，探讨了测量外延膜准确晶格常数的方法。认为必须考虑外延层和衬底间取向偏差在测量中引入的叠加效应，并予以消除。测试得到GaN外延层晶体的a方向晶格常数小于、而c方向晶格常数大于自由状态下体单晶的晶格常数，说明外延层处于压应力状态。压应力主要来源于晶格失配和热失配。更多还原

【Abstract】 In recent years, GaN-based optoelectronic materials and devices have been rapidly developed, however, there has not full studied in GaN thin films. Many theoretical and experimental studies should be focused on the GaN-based materials and properties, especially these problems affected industrialization. So far, almost all of the published papers are regarded on the density of threading dislocations in GaN. Many studies have been done on different approaches studied the density of threading dislocations of GaN, such as Transmission electron microscopy (TEM), X-ray diffraction(XRD), but the results which measured by these approaches are not consistency with luminescence.In this thesis, on the basis of analysis the advantages and disadvantages of the usual approaches, high-resolution X-ray diffraction was used to analyze the GaN layers grown on sapphire by metal-organic chemical vapor deposition (MOCVD), such as the crystal structures, the misorientation angle between the GaN epilayer and Sapphire substrate、 the accurate lattice constants of GaN films、 the bending radius of the wafers and stress of GaN films and dislocation densities . The main content of this thesis and some main conclusions are as follows:1、 The diffractograms(20/ω-scans) of all samples only have (00.2)、 (00.4) diffraction peak in the direct mode indicated that the GaN films are wurtzite structure and strongly c-oriented. The GaN thin films are not parallel Sapphire substrate and misorientation has exactly came into being between them. The measured c lattice constant by eliminated the instrument’s error is larger than that of body single crystal GaN which indicates that the films are under the compressive stress.2、 The measuring method of the accurate crystal constants was discussed basing on the substrate peak of the X-ray high intensity diffraction spectrum and the errors induced by misorientation must be deducted. The measured a lattice constant is less than that of body single crystal GaN and c is larger, which also indicates that the films are under the compressive stress. This compressive stress is derived from the lattice and thermal mismatch.3、 Misorientation was exactly assuredly came into being between the GaN epilayer and Sapphire substrate by X-ray high intensity mode diffraction measurement. The misorientation azimuth angle is nearly same with the miscut azimuth of sapphire更多还原