Light-facilitated ferroelectric switching in wurtzite crystals

Abstract

Wurtzite ferroelectrics combine large remanent polarization with full CMOS compatibility, positioning them as a leading platform for next-generation non-volatile memory. Their practical deployment, however, is hindered by an intrinsically large coercive field, rooted in the high energy barrier separating the polar wurtzite phase from the nonpolar hexagonal phase that mediates polarization switching. Here, using first-principles calculations, we propose an alternative, field-free strategy for lowering this barrier: above-bandgap electronic photoexcitation. Taking LaN as a representative wurtzite ferroelectric, we show that light induced carriers dramatically reduce the energy difference between the hexagonal intermediate phase and the wurtzite ground state, sharply reducing the energy barrier to ferroelectric switching. This effect originates from a photoinduced partial metallization of the polar phase, which screens the dipole-dipole interactions that stabilize ferroelectric order and thereby favors the competing nonpolar structure. The robustness of this mechanism is further confirmed for the rocksalt polymorph. Our results establish light as a powerful, non-invasive route to controlling ferroelectric switching in wurtzites, opening a path toward faster, lower-voltage, and more energy-efficient non-volatile memory technologies.