X-ray reflectivity and atomic force microscopy studies of MOCVD grown AI_xGa_(1-x)N/GaN superlattice structures

The grazing incidence X-ray reflectivity（GIXR） technique and atomic force microscopy（AFM） were exploited to obtain an accurate evaluation of the surfaces and interfaces for metalorganic chemical vapor deposition grown Al_xGa_1-xN/GaN superlattice structures.The X-ray diffraction results have been combined with reflectivity data to evaluate the layer thickness and Al mole fraction in the AlGaN layer.The presence of a smooth interface is responsible for the observation of intensity oscillation in GIXR,which is well correlated to step flow observation in AFM images of the surface.The structure with a low Al mole fraction（x = 0.25） and thin well width has a rather smooth surface for the R_rms,of AFM data value is 0.45 nm.     

MOCVD AlxGa1-xN/GaN超晶格结构的X射线反射谱与原子力显微研究

采用掠入射X射线反射谱技术与原子力显微技术对属有机化合物化学气相淀积生长的AlxGa1-xN/GaN超晶格结构的表面和界面进行了精确表征。结合高分辨率X射线衍射谱与反射谱数据分析获得外延层各层厚度与AlGaN层的Al摩尔组分。掠入射x射线反射谱的显著强度振荡与原子力显微镜所观察到的台阶流动形貌表明了平整的界面和表面的存在。研究发现,低Al组分（x=0.25）且阱宽小的样品界面与表面粗糙度最小,通过原子力显微技术得到的表面粗糙度均方根偏差为0.45nm。