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Hybrid III-V Semiconductor Nanowires on Silicon


On-chip quantum light sources on silicon photonic platforms have been the primary building block for miniaturization and scaling of integrated quantum photonic system. Epitaxial growth of III-V semiconductor quantum dots encapsulated in nanowires offers numerous advantages, such as high material quality, monolithic integration on lattice-mismatched substrates, nanoscale device dimension, and capability of forming axial or core/shell 3D heterostructure, which makes it a promising and versatile platform for building such non-classical light sources. In this dissertation, we first demonstrate III-V semiconductor quantum dots embedded in nanowires on silicon substrates. More specifically, InAsP quantum dot-embedded InP nanowires are grown vertically using vapor-liquid-solid (VLS) method on a silicon substrate with pre-positioned gold catalyst, in which the atomically sharp interfaces between the InAsP quantum dot and the surrounding InP nanowire are achieved. The sharp optical transition of excitonic and biexcitonic behaviors in silicon-transparent regime is observed, which can be potentially employed to build non-classical light sources for quantum communication and computation. However, for functional and practical applications, one of the major criticisms is that the III-V nanowires generally can grow only along (111) direction, which further limits the choice of substrates and impairs the compatibility with standard (001)-oriented silicon photonic platforms. Next, we overcome this critical challenge by integrating III-V nanowires on (001) silicon-on-insulator (SOI) platforms via catalyst-free selective-area epitaxy. This approach is enabled by exposing the {111} crystal planes from the (001) silicon substrates using wet-etching technique. In addition, as a proof-of-concept for on-chip photonic applications, an 1D nanowire array is demonstrated with photonic crystal cavity modes that are optically coupled to SOI waveguides on a standard silicon photonic platform. Lastly, the realization of practical quantum photonic chip relies on having electrical control of individual components. For this, we perform fundamental studies on a vertical nanowire heterojunction diode and a vertical nanowire LED. The robust and reliable device performance at room temperature makes III-V nanowires on silicon a potential platform for practical and functional device development. In summary, this dissertation demonstrates three key outcomes as a pathway toward monolithic integration of non-classical light sources on silicon photonic platforms. The experimental works moreover opens a new paradigm of crystal growth for various nanoscale devices that can be utilized in photonic, medical, biochemical, and mechanical fields.

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