Adsorption-controlled growth of BiFeO ₃ by MBE and integration with wide band

BiFeO ₃ thin films have been deposited on (001) SrTiO ₃, (101) DyScO ₃, (011) DyScO ₃, (0001) AlGaN/GaN, and (0001) 6H-SiC single crystal substrates by reactive molecular beam epitaxy in an adsorption-controlled growth regime. This is achieved by supplying a bismuth over-pressure and utilizing the differential vapor pressures between bismuth oxides and BiFeO3 to control stoichiometry in accordance with thermodynamic calculations. Four-circle x-ray diffraction and transmission electron microscopy reveal phase-pure, epitaxial films with rocking curve full width at half maximum values as narrow as 7.2 arc seconds (0.002002̊). Epitaxial growth of (0001)-oriented BiFeO ₃ thin films on (0001) GaN, including AlGaN HEMT structures, and (0001) SiC has been realized using intervening epitaxial (111) SrTiO ₃ / (100) TiO ₂ buffer layers. The epitaxial BiFeO ₃ thin films have 2 in-plane orientations: [112̄0] BiFeO ₃ || [112̄0] GaN (SiC) plus a twin variant related by a 180̊ in-plane rotation. This epitaxial integration of the ferroelectric with the highest known polarization, BiFeO ₃, with high bandgap semiconductors is an important step toward novel field-effect devices.