Observation of Photodielectric Effect in Aluminum Nitride Piezoelectric Films

Piezoelectric semiconductors hold great promise for the development of optoelectronic devices due to the presence of a photodielectric effect (PDE), which has been observed in perovskite ferroelectric ceramics. However, the PDE in wurtzite-structured aluminum nitride (AlN) and how light affects dielectric properties remain unexplored. Here, we observed PDE of AlN films in the low-frequency region around 20 Hz to 1 MHz. The permittivity (εr) increased after light irradiation, and the change in εr increased with larger photon energy, accompanied by an increase in dielectric loss (tan δ). For Sc0.15Al0.85N, the change in Δε was significantly larger compared to AlN, whereas the variation of tan δ became smaller. The PDE exhibited reversible light-induced switching of piezoelectric polarization, and the time required for εr to saturate under light illumination was shorter for Sc0.15Al0.85N than AlN. This work provides a fundamental understanding for photocontrolled piezoelectric properties for exploration of better piezoelectric semiconductors with photodielectric behavior.