基于三步脉冲生长方法制备的高质量非极性a面AlN模板特性的研究

Study on the Properties of High-quality Non-polar a-Plane AlN Template Prepared by the Three-step Pulse Growth Method

采用金属有机物化学气相沉积(MOCVD)技术及三步脉冲生长方法,在半极性r面(22ˉ04)蓝宝石衬底上成功制备了非极性a面(112ˉ0)氮化铝(AlN)模板,并对其结构和光学性质进行了系统研究。与采用传统单一固定温度及单步脉冲方法制备的非极性a面AlN模板相比,本方法制备的非极性a面AlN模板的晶体质量、光学性质和表面形貌均得到较大改善。实际上,通过可变温度及三步脉冲生长方法制备的非极性a面AlN模板,不仅其X射线摇摆曲线和A_(1)(TO)拉曼散射峰的半峰宽均显著减小,且在对应的紫外-可见吸收光谱中也观察到较强的相对透光率和陡峭的吸收边。在5×5μm^(2)的原子力显微镜检测区域内,相应的均方根值最小低至3.4 nm,且非极性a面AlN模板样品呈现优异的表面形貌和较少的表面形变。以上研究结果揭示了采用可变温度及三步脉冲生长方法能够有效地制备高质量的非极性a面(112ˉ0)AlN模板,而该AlN模板在AlGaN基III族氮化物的外延生长中起着至关重要的作用。

The structural and optical properties of the non-polar a-plane(112ˉ0) aluminum nitride(AlN)template grown on semi-polar r-plane(22ˉ04) sapphire substrate with three-step pulsed flow growth method in a metalorganic chemical vapor deposition(MOCVD)system are investigated extensively.It is found that the crystalline quality,optical property,and surface morphology of the a-plane AlN template grown by the three-step pulsed flow growth method featured with variable temperature are greatly improved as compared with the a-plane AlN template grown by conventional one-step pulsed flow growth method at a fixed temperature.In fact,besides the remarkably reduced full width at half maximum values of both the symmetrical X-ray rocking curve and the A_(1)(TO)Raman scattering peak,strong relative light transmittance and steep absorption edge are observed in the ultraviolet-visible absorption spectrum for the a-plane AlN template grown by the three-step pulsed flow growth method.Furthermore,a superior surface morphology and a decreased surface deformation are achieved with a root mean square value as small as 3.4 nm in an atomic force microscope detection area of 5×5μm^(2).These results reveal that the three-step pulsed flow growth method should be powerful to grow high crystalline quality non-polar a-plane(112ˉ0)AlN template which plays a crucial role in the epitaxial growth of the AlGaN-based III-nitrides.