Apr 7, 2025
2:15pm - 2:30pm
Summit, Level 4, Room 435
Sharad Mahatara1,Stephan Lany1
National Renewable Energy Laboratoty1
Sharad Mahatara1,Stephan Lany1
National Renewable Energy Laboratoty1
Power electronics are crucial for a sustainable energy future, especially in integrating renewable energy sources and electrification. Advances in ultra-wide bandgap materials like high Al-content Al
xGa
1-xN are essential for efficient power handling but need suitable substrates for lattice matching. Metallic TaC has been proposed as a virtual substrate for Al
xGa
1-xN heteroepitaxy, as (0001) Al
xGa
1-xN in the wurtzite structure matches the (111) rocksalt (rs) TaC lattice at
x ≈ 0.5. Here, we use first principles DFT to predict the formation of heterostructural rs-wz interfaces between TaC and AlN (GaN) films, using an algorithm to systematically enumerate possible stacking sequences within a few atomic layers near the interface. We determine the lowest energy structure for each combination of substrate termination (Ta or C), film nucleation (Al/Ga or N), and wz polarity (Al/Ga- or N-polar). We further express the total film sheet energy as a function of elemental chemical potentials and construct a "phase diagram" for the most likely structures to form under varying growth conditions. Electronic structure calculations for the most favorable structures predict band alignment, Schottky barrier heights, and interface density of states. Our results provide guidance for synthesis control of substrate-film bonding, film polarity, and resulting electronic properties for ultra-widegap Al
xGa
1−xN alloys on TaC substrates.