通过双中温AlN插入层提高半极性(1122)面AlN薄膜的表面形貌和晶体质量

Effects of Thickness of Dual Moderate-Temperature-Grown AlN Interlayers on Surface Morphology and Crystalline Quality of Semi-Polar (1122) AlN Epilayer

摘要:

利用金属有机化学气相沉积方法在蓝宝石衬底上生长了一系列具有双中温AlN插入层(MTG-AlN)的半极性AlN薄膜样品。中温生长的AlN插入层具有较大的表面粗糙度,形成了类似纳米级图形化衬底结构,能够有效阻断高温生长的半极性AlN样品中堆垛层错的传播,从而提高半极性AlN样品的表面形貌和晶体质量。通过原子力显微镜和X射线衍射仪的表征,研究了MTG-AlN插入层厚度在20~100nm之间的变化对半极性AlN样品的表面形貌和晶体质量的影响。结果表明,所有半极性AlN样品都具有[1122]取向。当插入的MTG-AlN中间层厚度约为80nm时,半极性AlN样品表面粗糙度显著降低,晶体质量明显改善。

Abstract:

A series of semi-polar (1122) AlN epilayers have been grown on (1010) m-plane sapphire substrates with the help of dual moderate-temperature-grown (MTG) AlN interlayers by metal-organic chemical vapor deposition (MOCVD). Significant improvements in both surface morphology and crystalline quality of the semi-polar (1122) AlN epilayers have been achieved with the insertion of the MTG-AlN interlayers due to the formation of nano-scale patterned substrate-like structure and the reduction in the basal-plane stacking faults and their associated partial dislocations. The effect of the variation in the thickness of the MTG-AlN interlayer ranged from 20 to 100nm was investigated in detail based on the characterization results of atomic force microscopy (AFM) and X-ray diffraction. It was revealed that all the semi-polar AlN epilayer samples were uniquely [1122]-oriented regardless of the variation in the thickness of the MTG AlN interlayer. It was found that the most remarkable reduction in surface roughness and the most notable improvement in crystalline quality could be obtained when the thickness for the inserted dual MTG-AlN interlayers was approximately 80nm.