As engineered nanoscale building blocks for more complex structures and devices, semiconductor nanowires are particularly intriguing due to the ability to form wires from a variety of materials with control over basic electronic properties and the beginnings of control over wire positioning and assembly. However, a broad range of issues pertaining to synthesis of semiconductor nanowire heterostructures, elucidation of nanoscale structure and electronic properties, processing into devices including contacts and controlled nanowire placement, and the optimal exploitation of unique electronic, transport, and optical behavior in nanowires for various device applications remain to be explored. The PI proposes a comprehensive investigation of the fundamental properties of semiconductor nanowires and their application in electronic and optoelectronic devices, focusing on the following device applications: (1) nanowire-based transistor structures that will offer either (a) extremely low-power, highspeed operation for future logic and memory applications or (b) operation at extremely high frequencies and power densities for microwave and mm-wave circuit applications; and (2) nanowire photodiodes incorporated into structures for (a) generation of terahertz radiation, or (b) multispectral imaging based on integration of different nanowire structures on a single chip. All represent potentially major breakthroughs in device performance or functionality, while sharing common fundamental issues in materials synthesis, characterization, and processing. The proposed team encompasses experts in materials synthesis, advanced characterization, materials processing, and electronic and optoelectronic devices and systems, thereby ensuring that materials and processing studies address the issues most relevant to the device and system applications, and that device designs exploit the full range of possibilities provided by advanced materials synthesis and processing.
Intellectual Merit: Fundamental issues in the physics of nanoscale systems and the integration of nanostructures into realistic, high-performance devices will be addressed by a highly accomplished, multidisciplinary team with an established, extensive record of successful collaboration. Research topics of interest will include synthesis of novel semiconductor nanowire heterostructures; nanoscale electronic structure and carrier transport behavior in nanowires; metallurgical, processing, and quantumconductance issues in contact formation; design of advanced nanowire-based transistor structures for computation and communications; and nanowire photodiodes for terahertz signal generation and multispectral imaging. A strong educational component is envisioned, entailing the development of new graduate course sequences aimed at a multidisciplinary student audience, a freshman seminar series, mentoring of undergraduate students, and interaction with secondary school students via the UCSD Preuss School, a Charter School serving high-ability but socioeconomically disadvantaged secondary school students in the San Diego Unified School District.
Broader Impact: The proposed program will yield new capabilities and insights in nanostructure synthesis, the physics of nanoscale structures, processing and assembly of nanostructures, and their applicability in realistic devices and systems that will have relevance not only for the device applications targeted here, but for research on semiconductor nanowires specifically, and solid-state nanostructures more generally. The potential areas of impact include future logic and memory systems, high-speed circuits for communications, and terahertz to infrared/visible imaging. Graduate students and postdoctoral researchers will be educated in a vertically integrated, multidisciplinary setting, with major new experimental facilities associated with Cal(IT)2 at UCSD providing new capability as well as a unifying umbrella for this and related activities. The development of graduate-level course sequences will further facilitate training of students in important emerging areas of science and technology, while the proposed courses and mentoring/outreach programs at the undergraduate and secondary school levels will help both to educate nontechnical students about scientific and technological issues and to encourage students to pursue advanced education and careers in science and engineering.
