The Role of Interface Band Alignment in Epitaxial SrTiO₃/GaAs Heterojunctions

Correlated oxides are known to have remarkable properties, with a range of electronic, magnetic, optoelectronic, and photonic functionalities. A key ingredient in realizing these properties into practical technology is the effective and scalable integration of oxides with conventional semiconductors. Unlocking the full spectrum of functionality requires atomically abrupt oxide-semiconductor interfaces and intimate knowledge of their potential landscape and charge transport. In this study, we investigated the electrical properties of epitaxial SrTiO₃/GaAs heterostructures by examining the band alignment and transport behavior at the interface. We employ X-ray photoelectron spectroscopy (XPS) to measure the barriers for electrons and holes across the interface and, through them, explain the transport behavior for junctions with n- and p-type GaAs. We further show qualitative evidence of the strong photoresponse of these structures, illustrating the potential of these structures in optoelectronic devices. These results establish the fundamental groundwork for utilizing these interfaces toward new devices and define their design space.