STUDY ONTHE GROWTH PROCESS AND THE BASICPROPERTIES OF QUANTUM DOTS USING II-VI GROUP COMPOUDS

本研究借由原位量测点形成过程中之镜面光束强度，探讨在ZnSe上成长CdSe点之机制。作为点生长方法，我们使用了分子束外延（MBE），其使用Se和Cd的交替分子束供应（ALS）。获得的结果如下。(1)ZnSe衬底上的CdSe量子点采用Stranski-Krastanow模式生长。只有在ZnSe缓冲层上生长的2 ML CdSe上的第三个CdSe单层变为点状。（2）低于3 ML的CdSe供应产生CdSe点，这是由于过量的Se吸附。也就是说，ALS生长不同于理想原子层外延（ALE）。Isp测量不能清楚地理解这一点。(3)CdSe点与ZnSe盖层和缓冲层的合金化。CdSe量子点嵌入ZnSe合金中，周围有nSe，但核心部分仍为CdSe。无帽CdSe点与ZnSe缓冲层形成合金，经过长时间热退火后，整个点成为ZnCdSe合金。(4)倾斜角和表面取向对点生长有很大影响。这一结果为进一步分析CdSe量子点的产生提供了依据。

This study is to investigate the growth mechanism of CdSe dots on ZnSe by means of in-situ monitoring the specular beam intensity during the dot formation. As the dot growth method, we used the molecular beam epitaxy (MBE) using the alternate molecular beam supply (ALS) of Se and Cd. Obtained results are as follows.(1) CdSe dots on ZnSe grow by Stranski-Krastanow mode. Only the third CdSe monolayer on 2ML CdSe grown on ZnSe buffer layer changes to dot. 2ML-CdSe layer remains as a wetting layer/(2)The CdSe supply below 3ML gives rise CdSe dots, which is due to the excess Se adsorption. That is ALS growth differs from ideal atomic layer epitaxy (ALE). This is not clearly appreciated by Isp measurement.(3) The alloying of CdSe dots with ZnSe cap layer and buffer layer. CdSe dots embedded in ZnSe alloys with surrounding nSe, but the core part remains as CdSe. Capless CdSe dot makes alloy with ZnSe- buffer, and the entire dot become ZnCdSe alloy after long thermal annealing.(4) The dot growth is strongly affected by the tilt angle and surface orientation. This result give an information for the detailed analyses of CdSe dot generation.