ZnCdSe量子点的MOCVD生长及其演变

利用应力释放模型计算了 Zn Cd Se/Ga As间的临界厚度 ,并以该临界厚度为基础 ,用 MOVCD设备在Stranski-Krastanow (S-K)生长模式下 ,外延生长了 Zn Cd Se量子点。用原子力显微镜和光谱测量的方法研究了量子点的演化过程。随着时间的推移 ,量子点发生了两种变化 ,即 Ostwald熟化过程和量子点的生成过程。另外 ,量子点由尖塔状逐渐演化为圆顶状。这种形状的变化可以用晶体生长模型进行解释。通过分析量子点样品的发光光谱 ,发现了两种发光机制 ,一种是零维量子点激子的发光 ,另一种是二维激子的发光。随着量子点生长完毕与加盖层之间间隔时间的增加 ,零维激子对二维激子发光的比值增加 ,且发光峰位明显红移。这从另一方面验证了由原子力显微镜直接观测到的量子点的演化过程

MOCVD Growth and Evolution of ZnCdSe Quantum Dots

ZnCdSe quantum dots were fabricated under Stranski Krastanow (S K) mode by metalorganic chemical vapor deposition (MOCVD). Previous to the growth, the critical thickness was calculated in terms of strain relaxation and the growth was then performed with the guidance of the calculation. the evolution of the QDs was also studied by atomic force microscopy (AFM) and spectroscopy. There appeared two kinds of variations in the QDs as time progresses, one is the Ostwald ripening process, the other is the dot formation process. Moreover, the shape of the dots changed from pyramid like to dome like, which was explained by the theory of crystal growth. By analyzing the photoluminescence spectra, two emission mechanisms were revealed, and they were thought to be the zero dimensional (0D) and 2D like excitons, respectively. With increasing the growth interruptions, the luminescence intensity ratio of the 0D to 2D like excitons increased, which gave further evidence of the evolution of QDs.