Atom-Scale Insights into III-V Semiconductor Nanowires

Abstract

As the feature size of MOSFET is scaling down to nano-size, series of problems need to be overcome to continue Moore’ Law, which seems an impossible task with traditional bulk Si technology due to the physical limitation and various negative effects being subject to small feature size. The critical issues for both further improving the devices’ performance and lowering their cost lie in the exploration of substitutions for Si and the control of morphological and compositional properties of materials. group III-V nanowires due to its unique properties are considered as the building block for next-generation electronic devices. To fulfill these commercial applications with group III-V nanowires, a fundamental and quantitative understanding of growth-structure-property relationships is central to applications where nanowires exhibit clear advantages. Therefore, this doctoral research systematically investigates three different semiconductor nanowires: Au-seeded, self-seed and planar nanowires, in terms of elemental, morphological and structural aspects by taking advantage of cutting-edge technique atom probe tomography, and endeavor to unveil the correlation between nanowires’ intrinsic properties and performance. Based on the atom probe findings, the growth mechanism of Au-seeded and self-seeded nanowire have been systematically discussed, and new model has been proposed to explain the phenomena on the basis of density functional calculation. Moreover, the doping distribution in planar nanowires has also been carefully investigated, and the results demonstrate that the dopants can diffuse into the substrate which subsequently degrade the device performance due to parasitic channel effect, and accordingly, suggestions have been given to optimize the planar nanowire growth for improved dopant distribution. The outcomes of this project are expected to theoretically support high-quality nanowire synthesis for specific applications.