Semiconductor nanowires: A versatile approach to nanoscale electronic and photonic circuit elements.

摘要

Semiconductor nanowires provide a unique interface between the macroscopic and microscopic world. Lengths in the tens of microns make it easy to form electrical contact and to observe and interact with them via optical signals, while diameters as small as a few nanometers allow them to address electrical and optical signals with extreme resolution, and to exhibit high sensitivity toward highly localized stimulus. The research in this thesis examines nanowire synthesis, classical and quantum carrier transport, and waveguiding and modulation of light, and is undertaken with a view toward developing the potential of nanoscale semiconductor materials as building blocks for integrated electronic and photonic systems.; The first project concerns indium arsenide nanowires (formed by metal nanocluster-catalyzed growth, using a laser ablation InAs source), in which quantum interference phenomena suggestive of an Aharonov-Bohm effect are evident in low-temperature magneto-conductance measurements.; In a second project, n-channel and p-channel single germanium nanowire field-effect transistors (FETs) were demonstrated, in which the current drive and transconductance meet or exceed those reported for recent planar Ge FETs. The Ge nanowires were synthesized via a multi-step chemical vapor deposition procedure involving in situ surface doping, and enabled the first demonstration of ohmic contacts, high transconductance, and comparable current drives for both n-type and p-type doping in the same nanowire material. Synthetic subtleties brought to light in this work have broad significance for the growth of doped or alloyed nanowire materials.; The third body of work involves the development and study of nanoscale photonic circuit elements made from cadmium sulfide and gallium nitride nanowire waveguides, in which the nanowires confine optical modes via dielectric contrast, and at the same time participate actively in optical signal transduction via semiconductor band edge transitions. Waveguides made from US nanowires, as well as assembled multi-wire structures, were shown to be capable of guiding visible, band-edge light around sub-wavelength bends with fairly low loss. Intra-nanowire electro-optic modulators were developed in both US and GaN, and in both cases were used to modulate optically-driven nanowire lasing without chirp.