Depth Resolved X-ray Scattering Topography for gallium nitride epitaxial layer on gallium arsenide substrate

我们提出的X射线散射形貌术已成功地应用于GaAs上InAs分子束外延、Si上金属有机化学气相沉积GaAs等晶格失配的异质外延层系中。该方法也适用于任何材料，并观察了Fe-3%Si单晶的取向分布、Al-4%Cu多晶焊接区的结构，和无定形橡胶型（复合材料）。我们的目标是获得GaN在GaAs上的深度分辨X射线散射形貌。为了达到这一目的，我们准备了（1）用动态衍射理论对X射线波场进行计算机模拟，（2）对GaAs衬底上GaN的结构进行研究，（3）对新的测量系统进行改造，我们用动态衍射理论对晶格失配的异质外延层进行了计算机模拟，我们测量了GaAs衬底上GaN的极小角X射线衍射，为了研究多晶型、纤锌矿和锌混合物的深度依赖晶体结构。虽然观察到了晶体结构的深度依赖性，但不能用对称性来解释。因此，我们通过测量倒易映射来研究该系统的结构分析。在纤锌矿只向一个[111]方向倾斜的薄膜中，我们得到了变形晶格常数的精确值。利用非对称衍射单色仪和同步辐射光源产生的平面波微束，可以获得更高的空间分辨率形貌。

X-ray scattering topography, which we proposed, has been successliMly applied to lattice-mismatched heteroepitaxial layer system, such as a molecular beam epitaxy grown on InAs on GaAs, metal-organic chemical vapor deposition grown GaAs on Si etc. This method applied any kind of materials, too, arid observed an orientation distribution of an Fe-3%Si single crystal, the structure of the welded region of Al-4%Cu polyciystals, and an amorphous rubber type (composite material). We aimed to obtain depthresolved X-ray scattering topography of GaN on GaAs. We prepared, in order to reach the aim, (1) computer simulation ofX-ray wave field by dynamical diffraction theory, (2) structural study of GaN on GaAs, (3) rebuilding of new measurement system.We have performed computer simulation for lattice mismatched heteroepitaxial layer by dynamical diffraction theory, it was indicated that epitaxial film calculation results are very different from bulk ones.We have measured extremely small angle X-ray diffraction for GaN on GaAs, in order to study depth-depend crystal structure about polymorphism, wurtzite and zinc-blend. Although depth-depend crystal structure was observed, the results were not be able to explain from symmetry. Therefore, we studied structural analysis of this system by measuring reciprocal mapping. In the film wurtzite was inclined to only one [lll] direction, we obtained exact value of deformed lattice constants.We built a new system including CCD camera. Near future, we will obtain a higher spatial resolution topography using a plane wave micro-beam, which were made by asymmetric diffraction monochromator and Synchrotron Radiation.