Current Rectification and Photo-Responsive Current Achieved through Interfacial Facet Control of Cu2O–Si Wafer Heterojunctions

Conductive atomic force microscopy (C-AFM) was employed to perform conductivity measurements on a facet-specific Cu₂O cube, octahedron, and rhombic dodecahedron and intrinsic Si {100}, {111}, and {110} wafers. Similar I-V curves to those recorded previously using a nanomanipulator were obtained with the exception of high conductivity for the Si {110} wafer. Next, I-V curves of different Cu₂O-Si heterostructures were evaluated. Among the nine possible arrangements, Cu₂O octahedron/Si {100} wafer and Cu₂O octahedron/Si {110} wafer combinations show good current rectification behaviors. Under white light illumination, Cu₂O cube/Si {110} wafer and Cu₂O rhombic dodecahedron/Si {111} wafer combinations exhibit the largest degrees of photocurrent, so such interfacial plane-controlled semiconductor heterojunctions with light sensitivity can be applied to make photodetectors. Adjusted band diagrams are presented highlighting different interfacial band bending situations to facilitate or inhibit current flow for different Cu₂O-Si junctions. More importantly, the observation of clear current-rectifying effects produced at the semiconductor heterojunctions with properly selected contacting faces or planes implies that novel field-effect transistors (FETs) can be fabricated using this design strategy, which should integrate well with current chip manufacturing processes.