Multiferroic LuFeO₃ on GaN, Studies of Band Offsets and a Polar-Polar Interface

The ability to integrate epitaxial ferroelectrics on GaN, an established wide bandgap semiconductor platform, has been recently demonstrated [Li et al, Advanced Materials Interfaces 5, 1700921 (2018)] by pulsed laser deposition (PLD) of Pb_xZr_1-xTiO₃. LuFeO_3, a room temperature ferroelectric and low temperature (~147K) multiferroic material, has been integrated with LuFe₂O₄ layers in a superlattice that demonstrated near room temperature (~281K) magnetoelectric multiferroic behavior [Mundy et al, Nature 537, 7621 (2016)]. Its hexagonal crystal symmetry makes it promising for epitaxial integration with III-nitrides. Here, we report the molecular beam epitaxy (MBE) growth, ferroelectricity, and band offsets of hexagonal LuFeO₃ on GaN. Piezoresponse force microscopy (PFM) results of LuFeO₃-n type GaN interface indicate ferroelectric switching behavior. X-ray photoelectron spectroscopy (XPS) of core levels of LuFeO₃-GaN interfaces was utilized to determine the valence band offset. Preliminary results indicate a valence band offset of ~1.3 eV. Assuming a bandgap of ~ 1 eV for LuFeO₃, this gives a conduction band offset of ~ 1 eV. These studies highlight a potential avenue of epitaxial LuFeO₃-GaN based multiferroic-semiconductor heterojunctions for memory and logic applications.