氧化处理的蓝宝石基片上沉积的ZnO/MgO多量子阱的结构及光学性质研究

Structure and optical properties of ZnO/MgO multi-quantum wells deposited on oxidated sapphire substrate

采用射频反应磁控溅射的方法,在经过氧化处理的Al2O3(0001)基片上制备了具有良好调制结构的ZnO/MgO多层膜量子阱.利用X射线反射率测量、X射线衍射分析、电子探针显微分析、原子力显微镜、透射光谱以及光致发光光谱等表征技术,研究了ZnO/MgO多量子阱的结构、表面形貌和光致发光等特性.XRD以及扫描的结果表明多层膜样品具有高c轴择优取向并且与蓝宝石基片有良好的外延关系.通过X射线反射率测量的结果得到多量子阱的调制周期,结合电子探针测得的Zn/Mg原子比求出了阱层的宽度在8·38nm至21·78nm之间.原子力显微镜测量结果表明样品的表面均方根粗糙随调制周期的减小而从6·4nm增加到21·2nm.低温光致发光光谱显示紫外发光峰对应于束缚激子的辐射复合,拟合给出激子激活能约30meV,并且在阱宽较小的样品中观测到了量子限域的斯塔克效应对应的发光峰.

ZnO/MgO multi-quantum wells with modulation structure are grown on oxidated Al_2O_3 （0001） substrates using radio-frequency reactive magnetron sputtering method. X-ray reflectivity and X-ray diffraction measurement,electronic probe,atom force microscopy,transmission spectrum and PL spectrum are used to characterize the samples. The XRD scan and phi-scan results show the films are highly （001） textured and have epitaxial relationship with the substrates. The width of quantum well is determined to be between 8.38 nm and 21.78 nm by XRR and EP MA. The AFM results show that the RMS roughness of the MQWs increases from 6.4 nm to 21.2 nm with the decrease of period of modulation. Low temperature PL spectrum shows the peak can be assigned to the radiative recombination of bound excitons,and the activation energy is estimated to be about 30 meV. The emission due to spatially separated carriers caused by quantum-confined Stark effect is also found in the spectrum of sample with smaller well width.