Giant Bulk Photovoltaic Effect in Crystal Orientation Restructured Quasi-Epitaxial BaTiO₃ Films on Silicon Substrates

The bulk photovoltaic (BPV) effect in ferroelectric (FE) materials enables the direct conversion and exchange of information between the optical and electrical domains in applications such as photonic computing and photodetection. Although the above-bandgap open-circuit voltage in the FE BPV effect permits a much higher photovoltage in comparison to the semiconductor PV effect, there are still challenges. For example, when requiring a reduction in the thickness of materials for device fabrication and integration, the photovoltage tends to diminish. In this paper, we demonstrate that interfacial strain-induced structurally orientated domains can enhance the BPV effect of FE films, with a 50 nm thick BaTiO₃ film, grown on a silicon substrate, shown to exhibit an open-circuit photovoltage of over 1.07 V - the highest reported value for traditional ferroelectric films under 300 nm thickness. This work offers new insights into the role of crystal orientation in FE BPVs as well as points to the potential use of ferroelectric materials in various photoelectrical applications, such as high-speed data processing and transmission in photonic computing systems, when integrated with silicon.