The role of titanium at the SrTiO3/GaAs epitaxial interface

• Single crystal SrTiO3 grown on GaAs with Ti interlayer by molecular beam epitaxy.
• Structural properties analyzed by x-ray diffraction.
• Structural properties analyzed by transmission electron microscopy.
• In-situ photoelectron spectroscopy (XPS) has been performed.
• We draw a growth mechanism bringing out the benefit of a Ti interlayer.

We study the role of a Ti surface treatment applied to the As-terminated GaAs (001) substrate surface prior to SrTiO3 (STO) epitaxial growth by comparing STO/GaAs samples prepared with and without Ti interlayers. Reflection high energy electron diffraction, transmission electron microscopy and x-ray photoelectron spectroscopy are used to assess the structural and chemical properties of the layers and interfaces. Without Ti interlayer, a polycrystalline TiGa compound is formed near the interface. It significantly degrades STO structural properties. A Ti interlayer efficiently prevents the formation of this unwanted compound by limiting As desorption from the GaAs substrate during STO growth. It improves significantly the structural quality of the oxide layer.