Understanding Quantum Defects in GaN

About This Grant

Nontechnical description: This project will investigate defects in the semiconductor gallium nitride with an eye toward sensing applications. While gallium nitride is already an important semiconductor for power electronics used in chargers and electric cars, it was also recently discovered that it contains individual defects that behave like single atoms that are interesting for quantum technologies. These defects have a property called spin that allows them to sense the magnetic field in their environment. Because the optical response of the defects also depends on the spin, one can use light to measure magnetic field in a tiny volume. This attractive behavior motivates a deeper investigation into the spin and optical properties of these defects, and an effort to understand how they may be engineered. This project will also help to educate students on science and technology. This includes training for undergraduate and graduate students. For high school level students, the team will help students to understand what an Engineering Physicist does and how that can enable an advanced workforce. Technical description: This project will probe the optical and spin levels of isolated defects in gallium nitride, seeking to discover their nature as well as how they are coupled together to enable optical spin readout. These experiments will include time-resolved optical measurements that seek to understand the rate of excitation and relaxation between different states of the defect depending on spin. In this work the team will study defects individually, examining defect-to-defect variations and which models of the optical properties can explain those variations. Also using the spin as a coherent probe of its local environment, the research team will investigate the electronic and nuclear spins that are nearby and thus seek to establish the structure and nature of the defect. For this purpose, they will use optically detected spin resonance, adapting measurement protocols that were developed for nuclear magnetic resonance and electron spin resonance. The research team will simultaneously investigate the materials conditions necessary to create and engineer these defects. Working with collaborators that grow gallium nitride, the team will research the doping, crystal growth face, and substrate combinations that encourage the formation of these defects, with the goal of controlling their creation and concentration. This investigation will lay the scientific and technical foundation for a quantum sensing platform that can be monolithically integrated with gallium nitride electronics and optoelectronics. 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.