Fully Epitaxial Ferroelectric ScAlN/GaN Heterostructures

In this work, we report on the demonstration of ferroelectricity in ScAlN grown by plasma-assisted molecular beam epitaxy (MBE) on GaN/sapphire substrates. Distinct polarization switching is unambiguously observed for ScAlN epilayers with Sc contents in the range of 0.14-0.36. Sc_0.20Al_0.80N, which is almost lattice-matched with GaN, exhibits a coercive field of ~ 4.2 MV/cm and a remnant polarization of ~135 mC/cm². After electrical poling, no obvious fatigue behavior can be found with up to 3 ×10⁵ switching cycles. The effect of as-grown lattice-polarity on the structural and ferroelectric properties has been studied in detail by controlling the heteroepitaxial relationship. Furthermore, we demonstrate the ferroelectric resistive switching in the ScAlN/GaN heterostructures, showing promising high-temperature operation capability. The realization of ferroelectric single-crystalline III-V semiconductors makes it possible to integrate high-performance ferroelectric functionality with well-established semiconductor platforms for a broad range of electronic, optoelectronic, and photonic device applications.