MSE PhD Prospectus Defense: Catherine Wang

MSE PhD Prospectus Defense: Catherine Wang

TITLE: FERROELECTRIC MATERIAL AND DEVICE PROPERTIES OF TERNARY ALUMINUM NITRIDE ALLOYS

ADVISOR: Enrico Bellotti, ECE, MSE

COMMITTEE: Masahiko Matsubara, ECE; Sahar Sharifzadeh, MSE, ECE; James Chapman, MSE, ME

ABSTRACT: Ferroelectric wurtzite aluminum nitride alloys have emerged as promising semiconductor materials for next-generation acoustic, electronic, memory, and electromechanical devices. Alloying aluminum nitride (AIN) with scandium (Sc), yttrium (Y), or boron (B) enables large polarization responses and ferroelectric switching while maintaining many of the advantages of Ill-nitride materials. However, the composition-dependent relationships among structure, polarization, piezoelectric response, switching behavior, and device performance remain incompletely understood, particularly for YAIN and BAIN. This work uses density functional theory (DFT) to evaluate composition-dependent lattice parameters, elastic response, spontaneous polarization, and piezoelectric coefficients. The results show that Sc and Y alloying expand the AIN lattice, reduce spontaneous polarization, and enhance piezoelectric response within the wurtzite stability range. In contrast, B alloying contracts the lattice, increases spontaneous polarization, and produces a weaker, non-monotonic piezoelectric enhancement. Polarization switching is also examined using solid-state nudged elastic band (ss-NEB) calculations. Preliminary results show that increasing B or Sc concentration lowers the intrinsic switching barrier, while different alloys exhibit distinct switching pathways. Overall, this work uses a theoretical framework for understanding ternary AIN-based ferroelectrics for polarization dependent devices.