CAREER: Unlocking Programmable Doping in Wide-Bandgap Materials

Nontechnical Description Modern society depends on efficient energy conversion across technologies that range from small motors to hyperscale data centers. These data centers can draw as much as 10 megawatts each. Thus, even small gains in power-converter efficiency translate into massive energy savings on the scale of terawatt-hours. A core challenge limiting progress in these systems is the inability to precisely control how and where dopants—impurities that determine electrical behavior—are introduced into semiconductors. Wide-bandgap semiconductors like gallium nitride and aluminum nitride offer superior performance compared to traditional silicon. However, their doping processes remain rigid and difficult to optimize. This research addresses that bottleneck by developing a programmable doping strategy. This is a way to insert dopants into already-grown semiconductor crystals with nanometer-scale spatial precision. This method removes the need for costly regrowth and allows electrical junctions to be formed wherever needed on a chip, improving energy efficiency while lowering production cost. The approach directly supports more efficient electrical inverters, power supplies, and next-generation computing systems. Beyond the technical contributions, the research integrates hands-on education and national outreach. A new university-level course module will introduce students to advanced doping and defect engineering in wide-bandgap materials. Undergraduate and high school students will participate in cleanroom-based experiments and modeling through established programs. Outreach efforts led by the Vanderbilt Institute of Nanoscale Science and Engineering will distribute classroom kits and digital content that bring these advanced concepts into K–12 classrooms. These combined activities broaden participation in semiconductor science and strengthen the pipeline of future researchers and engineers. Technical Description This research addresses a fundamental challenge in wide-bandgap semiconductor materials: achieving precise, high-efficiency dopant activation in ultrawide-bandgap systems such as aluminum-rich aluminum gallium nitride and aluminum nitride. As the bandgap widens, the formation of shallow, high-conductivity doped regions becomes more difficult due to increased dopant ionization energies, reduced solubility, and a tendency for compensating native defects to form. These factors limit junction sharpness and carrier concentration, constraining performance in high-voltage and high-frequency applications. The research develops a materials-level framework for programmable doping, which allows selective dopant introduction after crystal growth, decoupling doping from epitaxial constraints and enabling junction formation with nanometer-scale control. Three integrated approaches are used to overcome doping limitations: (1) finite-source diffusion enables spatially confined dopant delivery, (2) strain-assisted co-doping modifies defect formation energies and promotes dopant solubility, and (3) nanosecond pulsed-laser annealing activates dopants without damaging the crystal lattice. The project begins with gallium nitride as a well-characterized system, progressing to aluminum-rich alloys and ultimately aluminum nitride. The experimental workflow includes fabrication of doped junction structures, temperature-dependent Hall and capacitance-voltage measurements, and depth profiling via secondary ion mass spectrometry. Parallel multiscale modeling includes kinetic simulations of dopant diffusion and compensation behavior. Together, these efforts aim to produce predictive models for doping profile shape and activation efficiency based on material composition and processing parameters. The results are expected to establish general design principles for electrically active junctions in wide-bandgap semiconductors and inform new device architectures that drive improvements in energy efficiency, thermal management, and relia NSF Award ID: 2541951 | Program: 01002930DB NSF RESEARCH & RELATED ACTIVIT,01003031DB NSF RESEARCH & RELATED ACTIVIT,01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Mona ebrish | Institution: Vanderbilt University, NASHVILLE, TN | Award Amount: $369,607 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2541951 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2541951.html