Thermoelectric Properties of Self-Assembled Nanocristals in Semiconductor Matrix: Experiment and Theory

该项目的目标是继续对Si（GaAs）基质中SiGe（InGaAs）制成的无缺陷纳米晶体（量子点，QD）多层的热电性能进行实验和理论研究。研究将扩展到量子柱（QP），即相干嵌入SiGe（InGaAs）中的短纳米线。在目前的资助期间，我们已经通过实验证明，可以将Ge/Si多层膜的热导率精确控制到低至1 W/m. K的值。此外，我们已经从理论上预测，通过适当的工程量子点多层膜的属性，可以预期的功率因数值的增加。然而，实验测量的跨平面的热电势和电导率仍然很少。因此，我们将通过改变相关的结构参数，如层间距和掺杂水平，研究量子点和量子点的跨平面热电性能。结果将进行比较，计算使用一个现实的描述从原子模型和治疗的热电输运超出恒定弛豫率近似的电子结构。此外，将发展用于处理电子和声子系统中的组合非平衡效应的理论方法。这两种材料系统之间的比较和量子点和量子点之间的比较，预计将提供一个显着的进步的理解纳米结构半导体的热电性能。

Goal of this project is the continuation of the experimental and theoretical investigation of the thermoelectric properties of multilayers of defect-free nanocrystals (quantum dots, QDs) made of SiGe (InGaAs) in Si (GaAs) matrix. The investigations will be extended to quantum posts (QPs), i.e. short nanowires coherently embedded in SiGe (InGaAs). During the current funding period we have shown experimentally that it is possible to precisely control the thermal conductivity of Ge/Si multilayers down to values as low as 1 W/m.K. In addition, we have theoretically predicted that by proper engineering of the properties of QD multilayers, increased values of power factor can be expected. However, experimental measurements of cross-plane thermopower and electric conductivity are still scarce. We will therefore study cross-plane thermoelectric properties of QDs and QPs by varying relevant structural parameters, such as interlayer spacing, and doping level. The results will be compared to calculations using a realistic description of the electronic structure obtained from atomistic modelling and a treatment of thermoelectric transport beyond the constant-relaxation-rate approximation. Moreover, theoretical methods for treating combined non-equilibrium effects in both the electron and phonon system will be developed. The comparison between the two material systems and between QDs and QPs is expected to provide a significant advance on the understanding of the thermoelectric properties of nanostructured semiconductors.