Title: Novel alloys based on nitride semiconductors for ultraviolet light emitters and high-efficiency power electronics
Non-technical description: The nitride semiconductors, including gallium nitride (GaN), aluminum nitride (AlN), and indium nitride (InN) are the enabling materials for solid-state lighting based on light-emitting diodes. These materials are also used in power electronics, particularly for achieving power conversion (between alternating and direct current) with much higher efficiencies. In both areas, fabrication of high-quality nitride alloys with larger energy band gaps is desirable. In optoelectronics this will enable ultraviolet light emitters; in power electronics, higher voltage transistors. Computational theory, in tight collaboration with materials growth and characterization, will be used to accelerate these developments by exploring suitable alloy compositions and novel layer structures based on an atomistic, quantum-mechanical description of the materials. The results will have a strong impact on technologies ranging from optical data storage to water purification. Graduate and undergraduate students will benefit from the tight collaboration between theory and experiment. Outreach will take advantage of the Allosphere facility at the California Nanosystems Institute.
Computational and experimental efforts will be tightly coupled to address the development of materials and heterostructures based on wide-band-gap nitride semiconductors. First-principles calculations based on cutting-edge theoretical techniques will be performed, yielding the most accurate description currently available at the system sizes needed for modeling defects and heterostructures. Topics to be addressed include alignment of band structures at interfaces, polarization properties, identification of suitable dopants, the role of unintentional impurities, and devising strategies for avoiding detrimental defects. The growth will be carried out by plasma-assisted molecular beam epitaxy (MBE) or ammonia MBE. The materials to be explored include AlN and Al-rich AlGaN and InAlN alloys, as well as a largely unexplored novel alloy system, namely BAlN. Closing the loop between theory and experiment will provide deep understanding of fundamental atomic-level mechanisms and phenomena associated with synthesis and processing, benefiting the research training of graduate and undergraduate students.