Control of Excitons in AlGaN-Based Ultrawide Bandgap Heterostructures

Nontechnical description Deep ultraviolet (UV) light has many uses. For example, it is essential for public health applications such as water and air purification and sterilizing medical equipment. However, current UV technologies are inefficient and often rely on lamps containing mercury, a toxic material. This project seeks to develop the scientific foundation for a new generation of efficient deep UV light-emitting diodes. These are based on excitons, which are bound pairs of negatively and positively charged particles that can emit light efficiently. The work has the potential to enable more effective and environmentally friendly ultraviolet technologies while opening new opportunities in emerging fields such as quantum materials and advanced photonics. The project emphasizes education and workforce development. Undergraduate and graduate students receive training in materials science, including semiconductor growth and characterization. Outreach efforts, such as a partnership with the University of Michigan’s Museum of Natural History, broaden participation in science and engineering and inspire the next generation of researchers. Technical description This project will establish a fundamental understanding of excitonic physics in ultrawide-bandgap aluminum gallium nitride (AlGaN) heterostructures, a largely unexplored regime in condensed matter physics. The central scientific challenge is to determine how exciton formation, transport, stability, and recombination are governed by the combined effects of quantum confinement, strong Coulomb interactions, large internal polarization fields, and alloy disorder in Al-rich AlGaN. While excitons are expected to play an important role in deep-ultraviolet emission, current ultraviolet light-emitting heterostructures are designed primarily within free-carrier recombination frameworks and do not explicitly account for excitonic effects. The research will integrate epitaxial growth of AlGaN-based heterostructures, structural characterization, advanced optical spectroscopy, and electroluminescence measurements to probe excitonic behavior under both equilibrium and non-equilibrium conditions. Four interconnected tasks will investigate heterostructure synthesis, structural properties, exciton dynamics and transport, and electrically injected excitonic recombination. The resulting knowledge will establish a new framework for understanding light-matter interactions in extreme-bandgap semiconductors, advance excitonics into the deep-ultraviolet regime, and identify new pathways toward high-efficiency ultraviolet photonic materials and devices. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.