Integration of BaTiO₃/CoFe₂O₄ multiferroic heterostructure on GaN semiconductor

Epitaxial integration of BaTiO₃ (BTO)/CoFe₂O₄ (CFO) multiferroic heterostructure directly on GaN semiconductor was demonstrated using pulsed laser deposition. The domain matching epitaxy mechanism was revealed to be (111)[110] BTO//(111)[110] CFO//(0002)[1120] GaN. Spinel CFO thin films with a layer-by-layer growth mode on GaN not only served as the ferrimagnetic functional layer, but also as a buffer layer, inducing an epitaxial growth of perovskite BTO ferroelectric thin films on wurtzite GaN by greatly reducing lattice mismatch at the BTO/GaN interface. The designed BTO/CFO/GaN heterostructure displayed high crystallinity, dense microstructure and good interfacial state. More importantly, good ferroelectric properties for the BTO layer with a remanent polarization of 5.5 μC cm^-2 and magnetic properties for the CFO layer with a saturation magnetization of 169 emu cm^-3 at room temperature were also demonstrated. Thus, the epitaxial integration of high performance BTO/CFO multiferroic heterostructure with GaN could add more functional degrees of freedom for designing advanced microelectronic devices on a GaN semiconductor platform.