Physics and controlled properties of micro-and nano-scale granular semiconductor structures

(1)作为纳米尺度半导体结构的模型系统，我们生长和研究了自组织InAs量子点，并研究了它们的各种性质。具体来说，我们已经研究了一些在n-AlGaAs/GaAs异质结的通道电子被困在附近的通道嵌入的点，以及它们是如何被分散和去相的带电点。我们还研究了这些系统的存储器和光电探测器应用的潜力，因为被困在每个点的电子可以被擦除的带间光激发。量子点不仅可以被三次中和，而且还可以通过捕获空穴而带正电。电子弛豫从激发态到地面水平也进行了调查，并显示出很好地描述极化子效应。(2)为了拓展颗粒半导体结构的研究前沿，我们研究了在其他材料系统中形成的一系列点。特别是，嵌入GaAs量子阱中的AlGaSb点被示出为诱导量子环态，因为电子被带正电的II型点系统束缚。由InP岛在InGaAs阱上形成的应变点被发现显示出独特的光致发光光谱，这是由太赫兹辐射调制。讨论了它们的器件应用。

(1) As a model system of nano-scale semiconductor structures, we have grown and investigated self-organized InAs quantum dots and studied their various properties. Specifically, we have examined how some of the channel electronics in n-AlGaAs/GaAs heterojunctions are trapped by dots embedded in the proximity of the channel and how they are scattered and dephased by charged dots. We have examined also potentials of these systems for memory and photodetector applications, as trapped electrons in each dot can be erased by interband photo excitations. Dots can not only third neutralized, but also positively charged by trapping positive holes. Electron relaxations from the excited states to the ground level are also investigated and shown to be well described by polaron effects.(2) To expand the research forefront of granular semiconductor structure, we have studied a series of dots formed in other material systems. In particular, AlGaSb dots embedded in GaAs quantum well is shown to induce a quantum ring state, as an electron is bound by a positively charged typeII dot system. Strained dots formed by InP islands on InGaAs well are found to show unique photo luminescence spectra, which are modulated by tera hertz radiations. Their device applications are discussed.