The last two decades witnessed revolutionary advances in electronics and photonics by moving from ~1 electron Volt gap semiconductors (Silicon, Gallium Arsenide) to ~3 electron Volt Gallium Nitride and Silicon Carbide. This enabled energy-efficient light emitting diodes as replacement of incandescent bulbs, high-voltage transistors that are cutting down wasted energy in electrical devices and machinery, and significantly expanded our fundamental knowledge of the materials science of semiconductors. Similar major advances are expected by aiming at extreme-bandgap semiconductors with energy gaps almost twice of that of the wide-bandgap semiconductors. In addition to the new science, such materials should enable advances in healthcare and monitoring by creating deep-ultraviolet light-emitting diodes and lasers, and by significantly improving the efficiency and capability of semiconductors for electrical power conversion.
Investigation of extreme-bandgap semiconductor materials with gaps of ~5-6 electron Volts has the potential to seed vast application arenas, and simultaneously advance the fundamental materials science and the physics of materials. The goal of this proposal is to develop the materials science of extreme bandgap semiconductors: Boron Nitride, Aluminum Nitride, their alloys and their heterostructures, and to investigate their properties for future applications in power electronics, deep-ultraviolet emitters, and more. Guided by rigorous mathematical and first-principles theory and modeling, the 4-investigator team will explore fundamental questions regarding epitaxial growth, polarization-induced conductivity control, band anti-crossing in highly mismatched materials, effects of isotope engineering on electronic and thermal transport. The proposed research project has the potential to be transformative in the field of materials science and condensed matter physics under the umbrella of the Materials Genome Initiative because the research thrusts will develop: first-principles predictive theory of electronic, optical, and thermal properties of these materials, epitaxy of these new semiconductors, isotope alloys and heterostructures, novel methods for controlling conductivity, understanding and control of the interplay of competing 3-dimensional vs 2-dimensional crystal phases, understanding of ultra high-field optical, electronic, thermal phenomena, of cation band-anticrossing physics, novel paradigms of isotope (neutron) engineering of optoelectronic, solid-state qubit, Cooper pairs, and thermoelectric properties. The proposed project will result in the training of graduate students in a fascinating emerging field of extreme bandgap semiconductor material science, with their many fundamental electronic, optical, and thermoelectric properties. In addition to expanding existing outreach programs, new activities with a special focus on high-school students and underrepresented groups via Research Experiences for Teachers programs and direct visits for in-class demonstrations are proposed. That the team is distributed between Cornell, Michigan, and Stanford with complementary expertise will be exploited by regular exchange of graduate students for experiments, as well as theory and modeling work, to foster a truly collaborative mindset in the project. The dissemination of research by journal publications, presentations at conferences, its inclusion in courses taught by the invsetigators, and online (e.g. nanoHub) will make possible the outreach of the research results to the widest possible audience.
