用X射线衍射法测定氮化镓马赛克结构中的面内扭转角

Ⅲ-Ⅴ族氮化物半导体材料在发光二极管、激光器和探测器方面有着广泛的应用,采用高分辨X射线衍射来测定用金属有机化学气相沉淀法在蓝宝石衬底上生长的氮化镓外延层马赛克结构的扭转角,分别研究了(0002)、(1013)、(1012)、(1011)、(2021)五个面的X射线摇摆曲线,并且用Pseudo-Voigt方程拟合每一个面的摇摆曲线,我们利用外推法很方便地测得氮化镓外延薄膜的面内扭转角。另外我们采用同步辐射X射线掠入射衍射对样品进行(1100)面反射φ扫描直接测得面内扭转角,对第一种方法进行验证,两种方法测量结果相同。从而提供一种简单、方便的GaN外延层的面内扭转角的测试方法,为深入研究GaN材料奠定良好基础。     

Mosaic Structure Evolution in GaN Films with Annealing Time Grown by Metalorganic Chemical Vapour Deposition

We investigate mosaic structure evolution of GaN films annealed for a long time at 800℃ grown on sapphire substrates by metalorganic chemical vapour deposition by high-resolution x-ray diffraction. The result show that residual stress in GaN films is relaxed by generating edge-type threading dislocations （TDs） instead of screw-type TDs. Compared to as-grown GaN films, the annealed ones have larger mean twist angles corresponding to higher density of edge-type TDs but smaller mean tilt angles corresponding to lower density of screw-type TDs films. Due to the increased edge-type TD density, the lateral coherence lengths of the annealed GaN films also decrease. The results obtained from chemical etching experiment and grazing-incidence x-ray diffraction （GIXRD） also support the proposed structure evolution.