Fabrication of semiconductor nanostructures assuming enhanced magneto-optical effects and control of their magnetism by irradiation of light

利用分子束外延（MBE）技术在ZnTe（001）表面制备了CdTe和Cd_（1-x）Mn_xTe自组织点。在本研究项目中，我们进行了以下两个主题。(1)通过在混合晶体上生长点来改变由于势垒层引起的电子和空穴的限制能量（带隙工程）（2），形成其中重复生长点层和势垒层的结构（点超晶格），如下面详细描述的。(1)通过改变势垒层实现带隙工程我们在（Zn，Mg）Te混晶上生长了自组织的CdTe点，代替ZnTe。在光致发光测量中，发现与ZnTe上的点相比，发光强度的温度依赖性显著改善，抑制了发光的热猝灭。这被认为是由于t的增加增强了电子空穴对的约束所致 关于我们 势垒层的带隙能量。此外，我们还用类似的方法在（An，Mg）Te层上生长了（Cd，Mn）Te点。在磁光致发光测量中，我们观察到了由于巨大的塞曼分裂而引起的激子发射能量的红移，这种红移的大小与理论计算相一致。(2)点超晶格我们制备了Cd（Mn）Te点层和ZnTe势垒层经过几十次循环堆叠而成的超晶格结构。在PL测量中，我们观察到两条发射线，与具有点单层的样品不同。认为高能量谱线起源于单个点的孤立能级，低能量谱线起源于相邻点层中点之间的相关能级。对一系列不同势垒层厚度样品的PL测量结果证实了这一点，其中低能谱线的发射能量随势垒层厚度的变化而发生系统的偏移。少

We have fabricated self-organized dots of CdTe and Cd1-xMnxTe on ZnTe(001) surface by molecular beam epitaxy (MBE). In the present research project, we have performed the following two topics. (1) change the confinement energy of electrons and holes due to the barrier layer by growing the dots on the mixed crystal (band-gap engineering) (2) make the structure in which the dot layer and the barrier layer are grown repeatedly (dot superlattice), as the details are described in the following.(1) Band-gap engineering by changing the barrier layerWe have grown self-organized dots of CdTe on the mixed crystals of (Zn, Mg)Te, in place of ZnTe. In the photoluminescence measurement, it was found that the temperature dependence of the luminescence intensity was improved significantly, with the suppression of the thermal quenching of the luminescence, compared to the dots on ZnTe. This is considered to be caused by the enhancement of the confinement of electron-hole pairs due to the increase of t … More he band-gap energy of the barrier layer. In addition, we grew (Cd, Mn)Te dots on (An, Mg)Te layer in the similar method. In the magneto-PL measurement, we observed the red-shift of the exicitonic emission energy due to the gigantic Zeeman splitting, the amount of this red-shift was found to be consistent with the calculation.(2) Dot superlatticeWe have fabricated the superlattice structure in which the Cd(Mn)Te dot layer and ZnTe barrier layer were stacked with several tens of cycles. In the PL measurement, we observed two emission lines, differently from the sample with the dot single layer. It is considered that the higher-energy line originated from the isolated level of the individual dots and the lower-energy line originated from the correlated level between the dots in the neighboring dot layers. This assignment was confirmed from the results of the PL measurement on a series of sample wiath different thickness of the barrier layers, in which the emission energy of the lower-energy line was shifted systematically with the barrier thickness. Less