Understanding the Luminescence Efficiency of Silicon Quantum Dots

到目前为止，硅量子点的很大一部分光学性质要么仍然存在争议，要么完全未知，要么还在实验范围之外。该合作项目旨在阐明获得0维硅纳米结构光学性能的物理机制和极限的全面图像所需的几个重要性质。这项研究的动机有两个：一方面，基础半导体科学总体上将受益于对间接量子点(如硅)的尺寸效应的全面了解，当尺寸降至激子玻尔半径以下时，这种效应就会发生。然而，除了这种有充分理由的学术兴趣外，硅代表着技术上最重要、几乎无处不在的半导体。微电子工业的大刀阔斧的小型化正在逐步将有源硅体积缩小到量子限制效应开始发挥主要作用的尺寸范围。因此，广泛的知识是强制性的，包括这种相邻量子点的串扰。对于自支撑的Si量子点，其发光效率可以很容易地达到25%，甚至可以达到50%。与10-5的体硅量子产额相比，尺寸减少到5纳米，打开了一个全新的应用世界的大门。目前，硅光电子学能够修改、引导、切换和探测光，但它不能有效地从电能中产生光。然而，光电子学中的光源通常是由III-V半导体制成的，这些半导体不能在材料层面上集成到微电子电路中(硅是许多III-V材料的掺杂剂，这些材料大多是硅的中间禁带缺陷态)。实际上，在例如光芯片通信可以完全由硅基材料制造之前，还有很长的路要走。但可以想当然地认为，硅纳米结构将是这一技术演变的关键点。因此，深入研究硅量子点的基本光学性质和光学性能的主要极限具有重要意义。我们将详细研究以下目标：(1)硅量子点的吸收截面，(2)硅量子点的量子产额，(3)介质基质与硅量子点的相互作用。

Significant part of the optical properties of Si QDs is either still under controversial debate or completely unknown or was out of experimental reach up to now. This cooperation project aims to clarify several important properties that are required to obtain a comprehensive picture of the physical mechanisms and limits of the optical performance of 0 dimensional silicon nanostructures. The motivation for this study is two-fold: On the one hand, fundamental semiconductor science will benefit in general from a comprehensive understanding of the size effects in indirect quantum dots such as Silicon that occur when the dimensions are reduced below the exciton Bohr radius. However, apart from this well justified academic interest, silicon represents the technologically most important and virtually omnipresent semiconductor. The aggressive down-scaling of microelectronics industry is progressively reducing the active silicon volumes into a size range where quantum confinement effects start to play a major role. Hence, extensive knowledge is mandatory including the cross-talking of such adjacent quantum dots. For free standing Si QDs the light emission efficiency of Si QDs can easily reach 25% and even ~50% were reported. Compared to the bulk Si quantum yield of 10-5 the reduction of the dimensions to 5 nm opens a gate into a completely new world of applications. Currently, silicon optoelectronics is able to modify, guide, switch and detect light but it is not able to efficiently generate light from electricity. However, the light sources in optoelectronics are often made of III-V semiconductors which cannot be integrated on the material level into microelectronic circuits (Si is a dopant for many III-V materials and those are mostly mid-gap defect states in Si). Realistically, there is still a long way to go until e.g. optical on-chip communication can be solely fabricated from Si-based materials. But it can be taken for granted that Si nanostructures will be the pivotal point of this technology evolution. Therefore, intense research on fundamental optical properties and the principal limits of the optical performance of Si quantum dots is important. In detail the following objectives will be investigated in details: (1) Absorption Cross Section (ACS) of Si QDs, (2) Quantum Yield of Si QDs, and (3) Interaction of the Dielectric Matrix with Si QDs.