Crossover between bulk and interface photovoltaic mechanisms in a ferroelectric vertical heterostructure

• Main Authors: Abdelsamie, Amr, You, Lu, Wang, Le, Li, Shuzhou, Gu, Mingqiang, Wang, Junling
• Other Authors: School of Materials Science and Engineering
• Format: Article
• Language: English
• Published: 2023
• Subjects: Engineering::Materials; Ferroelectrics Materials; Inversion Symmetry
• Online Access: https://hdl.handle.net/10356/164434
• Institution: Nanyang Technological University

The bulk photovoltaic (BPVE) effect in crystals lacking inversion symmetry offers great potential for optoelectronic applications due to its unique properties, such as above-band-gap photovoltage and switchable photocurrent. Because of their large spontaneous polarizations, ferroelectric materials are ideal platforms for studying the BPVE. However, identifying the origin of an experimentally observed photovoltaic response is often challenging due to the entanglement between bulk and interface effects, leading to much debate in the field. This issue is particularly pronounced in vertical heterostructures, where the two effects are comparable. Here, we report crossover between bulk- and interface-dominant responses in vertical BiFeO3 heterostructures when changing the photon energy. We show that well-above-band-gap excitation leads to a bulk photovoltaic response, but band-edge excitation requires interface band bending to separate the photocarriers. Our findings not only help to clarify contradicting reports in the literature, but also lay the foundation for a deeper understanding of the ferroelectric photovoltaic effect and its applications in various devices.