Physics / mechanism
AlScN is a wurtzite-structure piezoelectric and ferroelectric thin film formed by substituting Sc onto Al sites in AlN. Scandium doping (typically 20–43 at% Sc) dramatically increases the piezoelectric coefficient (e₃₃) from ~1.5 C/m² in pure AlN to >4 C/m² at ~40% Sc, and enables ferroelectric switching absent in AlN. Electromechanical coupling (kt²) reaches 10–20%, versus 6–7% for AlN. Bulk acoustic resonator (BAR/FBAR) devices using AlScN now target frequencies from 3–30 GHz with Q-factors >1000. CMOS-compatible deposition via reactive co-sputtering is established; uniformity and phase-purity at high Sc concentrations remain active engineering problems. Ferroelectric memory (FeMEM) and neuromorphic applications are emerging, with coercive fields ~5 MV/cm.
Competitive landscape
AlScN competes primarily with PZT, LiNbO₃, and pure AlN in piezo/ferroelectric applications. GaN-on-Si and BaTiO₃ are adjacent in RF and memory respectively.
| Material | kt² | CMOS compat. | Ferroelectric |
|---|---|---|---|
| AlN | ~7% | Yes | No |
| AlScN | 10–20% | Yes | Yes (>30% Sc) |
| PZT | 25–35% | No (Pb) | Yes |
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.