Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Electrical and Computer Engineering

First Advisor

Chen Yang

Committee Chair

Chen Yang

Committee Co-Chair

Timothy D, Sands

Committee Member 1

Minghao Qi

Committee Member 2

Xianfan Xu


Semiconductor nanowires synthesized via the vapor-liquid-solid (VLS) mechanism have attracted extensive research interest in recent years owing to their unique structure as a promising candidate for the future electronic devices. Germanium and silicon nanowires, in particular, are compatible with the current silicon-based technology via direct assembly. However, one of the main challenges for the successful nanowire application in large-scale is the lack of the method for obtaining nanowires in desired positions and directions. Therefore, the comprehensive, systematic understanding of epitaxial nanowire growth and the more suitable method to align nanowires on novel structure are required. In this work, the synthesis of direction and position controlled VLS germanium and silicon nanowire on silicon substrate and its application in the unique structure will be introduced. First, the growth of heteroepitaxial germanium nanowires on silicon substrate is shown. The annealing temperature prior to following germanium nanowire growth should be lower than the eutectic temperature of substrate-catalyst for the heteroepitaxial growth of germanium nanowire. Second, the homoepitaxially vertical silicon nanowires are grown on silicon substrate through the consideration of the catalyst size and additional diborane dopant gas flow. As the flow of impurity diborane is required at the beginning of synthesis, the modulation-doping method creates the vertically aligned silicon nanowire with less doped or intrinsic part in the stem structure. Third, horizontal arrays of silicon nanowires on the unique trench structure are demonstrated. This planar alignment of nanostructures are realized into the surrounding-gate eld eect transistor (FET) using the nanolithographic techniques.