Epitaxial integration of (0001) BiFeO3 with (0001) GaN

Epitaxial growth of (0001)-oriented BiFeO3 thin films on the (0001) surface of GaN has been realized using intervening epitaxial (111) SrTiO3/(100) TiO2 buffer layers. The epitaxial BiFeO3 thin films have two in-plane orientations: [1120]BiFeO3(parallel sign)[1120]GaN plus a twin variant related by a 180 deg. in-plane rotation. BiFeO3 shows an out-of-plane remanent polarization of ∼90 μC/cm2, which is comparable to the remanent polarization of BiFeO3 prepared on (111) SrTiO3 single crystal substrates. The orientation of BiFeO3 realized on GaN provides the maximal out-of-plane polarization of BiFeO3, which is equivalent to a surface charge of 5x1014 electrons/cm2