淀积在不同小倾角蓝宝石衬底的n型GaN的研究

Investigation of n-type GaN deposited on sapphire substrate with different small misorientations

采用金属有机物化学淀积技术在不同倾角(0°—0.3°)的蓝宝石衬底上外延n型GaN.通过原子力显微镜观察到n型GaN均呈台阶流生长模式,0.2°和0.3°倾角衬底的n型GaN表面台阶朝向相同、分布均匀,明显地看到在0°倾角衬底的n型GaN表面由台阶重构直接导致的台阶朝向随机分布、疏密不匀的形貌.电子背散射分析表明,在0°倾角衬底的n型GaN外延层的应力随外延厚度增加而增加,而0.2°和0.3°倾角衬底的n型GaN外延层的应力没有明显的变化.电学和光学特性研究表明,0.2°和0.3°倾角衬底的n型GaN有较高的电子浓度和较低的黄光带与近带边强度之比.

The n-type GaN films have been grown on c-plane sapphire with different small misorientation（0°—0.3°）by metal-organic chemical vapor deposition.It was observed by atomic force microscopy that the n-type GaN has the step flow growth mode,the flow steps of the n-type GaN surface are uniformly distribution on 0.2° and 0.3° misorientation sapphire substrate,it was observed clearly that random and poor distribution of the flow steps was caused by the step reconstruction on 0° misorientation sapphire substrate.The image quality parameter of electron back-scatter diffraction indicated that the strains increase as the n-type GaN epilayer thickness increases on 0° misorientation sapphire substrate but do not vary obviously on 0.2° and 0.3° misorientation sapphire substrates.Electrical and optical properties demonstrated the n-type GaN grown on the 0.2° and 0.3° misorientation sapphire substrates have higher electron concentration and lower ratio of the intensity of yellow band to near band edge.