Energetic stability of SrTiO3 on GaAs(001) interfaces

The successful growth of epitaxial SrTiO$_{3}$ (STO) film on Si substrate using Molecular Beam Epitaxy (MBE) has proved that it is feasible to monolithically integrate the functional oxides with high mobility compound semiconductors [1,2]. While STO has been also deposited on GaAs without amorphous interfacial layers, the exact interface structure has been controversial; while Scanning Transmission Electron Microscopy (STEM) analysis indicates As/Sr interface layers , X-ray diffraction (XRD) measurement shows signs of Ga/SrO interface. Using ab initio calculations, we demonstrate that forming a fully oxidized layer directly on top of GaAs substrate is thermodynamically unstable. Instead, an oxygen-depleted Sr metal layer stabilizes the SrTiO$_{3}$/GaAs interface, in accordance with STEM measurement. We also show that the interface structure observed by XRD is possible under oxygen-rich conditions. The identification of different interface structures and the corresponding growth conditions can be useful for development of growth processes of oxide/semiconductor heterostructures. \\[4pt] [1] R. Contreras-Guerrero et al, J. Cryst. Growth 378, 238 (2013)\\[0pt] [2] R. F. Klie et al, Appl. Phys. Lett. 87, 143106 (2005).