Research on spatially and temporally resolved spectroscopy of semiconductor quantum structures by using ulta small probe light

在这个项目中，我们试图建立光谱技术来评估微观界面粗糙度，并在不受结构波动影响的情况下表征量子结构的固有光学性质。作为一项技术，我们开发了联合收割机局域探测光谱，使用显微镜的物镜透镜和光刻技术在样品顶部制作小窗口，从而提高空间分辨率。我们选择了由化合物半导体制成的量子结构，研究了这些量子结构以提高电学和光学器件的性能。通过减小诸如量子线和量子点的特征尺寸，尺寸波动对性质的影响变得显著。这解释了为什么我们选择量子结构，我们发现，在InGaAs/GaAs量子威尔斯，一些微观的势波动捕获的局域激子，这是不能检测到的宏观光致发光，可以检测到我们的技术。通过测量生长温度的依赖性，我们澄清，生长温度的增加导致恶化的界面粗糙度由于在表面偏析，然而，界面粗糙度相比，在较低的温度下生长的样品得到改善。此外，通过对掺杂调制的量子点施加电场，成功地观测到量子点中的带电激子，并控制了带电状态。此外，通过将超薄膜作为电子的定域中心插入到量子点中，创造了新的量子结构，成功地大幅提高了间接半导体的发光效率。我们发现量子点的堆叠极大地改变了生长模式。作为下一步，我们将把我们的光谱技术应用于这些量子结构，并澄清它们的微观结构和机制，以提高发光效率。

In this project, we have tried to establish spectroscopic technique to evaluate microscopic interface roughness, and to characterize inherent optical properties of quantum structures without being affected by structural fluctuations. As a technique, we exploited to combine local probe spectroscopy to use objective lens for microscope and lithography technique to fabricate small window on top of the sample, leading to improved spatial resolution.We selected quantum structures made from compound semiconductors, which are studied to improve electrical and optical device performance. By reducing the feature sizes such as quantum wires and quantum dots, the impact of the size fluctuations on the properties becomes significant. This explains why we selected the quantum structures.We found that localized excitons trapped by some microscopic potential fluctuations in InGaAs/GaAs quantum wells, which are not detected by macroscopic photoluminescence, can be detected by our technique. By measuring growth teroperature dependence, we clarified that the increase of the growth temperature lead to the deterioration of the interface abruptness due to the In surface segregations, however, the interface roughness is improved compared to the sample grown at lower temperatures. In addition, we succeeded in observing charged excitons in quantum dots and controlling the charged states by applying electric field to modulation-doped quantum dots.Furthermore, we tried to create novel quantum structures to insert ultra thin film as a localized center for electrons, and succeeded in improving drastically improve the luminescence efficiency of indirect semiconductors, and we found that stacking of quantum dots greatly modify the growth mode. As a next step, we will apply our spectroscopic technique to these quantum structures and clarify their microscopic structures and mechanisms for improved luminescence efficiency.