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 (ϵ_r) increased after light irradiation, and the change in ϵ_r increased with larger photon energy, accompanied by an increase in dielectric loss (tan δ). For Sc_0.15Al_0.85N, 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 ϵ_r to saturate under light illumination was shorter for Sc_0.15Al_0.85N than AlN. This work provides a fundamental understanding for photocontrolled piezoelectric properties for exploration of better piezoelectric semiconductors with photodielectric behavior.