Control of Optical Transitions with Quantum Microstructures of Indirect Semiconductors

我们研究了具有原子控制超结构的间接半导体的光学性质。通过观察Si/纯Ge/Si量子阱中Ge覆盖率的增加对孤岛发射的限制效应和发展，确定了孤岛形成的起始时间为3.7个单层。观察到了岛屿相关发射的量子限制效应，表明岛屿具有“量子点”特征。该岛对周围的材料产生了不均匀的应变场，并调制了电势。平面透射电子显微镜、激子-激子相互作用增强以及能带边缘态密度的增加证明了台阶边Ge“量子线”的形成。为了改善间接半导体的光学性质，发展了一种新型的半导体超结构--邻近约束结构(NCS)，并成功地应用于SiGe和AlGaP基超结构中。特别是，在SiGe/Si体系中，没有声子参与的发光被选择性地增强，显示了NCS作为光发射体的潜力。

We investigated optical properties of indirect semiconductors with atomically controlled superstructures. By observing confinement effect and development of island-related emission with incerasing Ge coverage in Si/pure-Ge/Si quantum wells, the onset of the island formation was determined to be 3.7 monolayrs. Quantum confinement effect of island-related emission was clearly observed, demonstrating that the islands have "quantum dot" character. The island was found to generate inhomogeneous strain-field to the surrounding materials and to modulate potential. Formation of the Ge "quantum wire" at the step-edge was evidenced by plan-view transmission electron microscopy, enhanced exciton-exciton interactions, and incerased density of states at the band edge. A novel semiconductor superstructure, "Neighboring Confinement Structure (NCS)", to improve optical properties of indirect semiconductors was developed and successfully applied to SiGe-and ALGaP-based superstructures. Particularly, in the case of SiGe/Si system, luminescence without phonon participation was selectively enhanced, demonstrating the potential of NCS as light emitters.