Wettability effects of graphene oxide aqueous solution in photodetectors based on graphene oxide/silicon heterojunctions via ultraviolet ozone treatment

Abstract

We report the wettability effects of graphene oxide (GO) aqueous solution on the electrical and photoresponse properties of GO-silicon (Si) photodetectors via ultraviolet ozone (UVO) treatment. GO-Si vertical heterojunctions were fabricated using a spray-coating method. In the GO/p-Si heterojunctions without UVO treatment (GO/p-Si), an island-like assembly of GO sheets was formed, indicating that a GO stacking structure may have an island shape on the substrate due to partial surface coverage. In contrast, for those with UVO treatment (GO/UVO-p-Si), a relatively more close-packed GO deposition may occur due to the more hydrophilic property of the substrate surface, leading to the full surface coverage of the p-Si surface. Photodetectors based on GO/p-Si and GO/UVO-p-Si heterojunctions exhibit distinct electrical and photoresponse properties. The GO/UVO-p-Si-based devices showed a higher photo-to-dark current ratio, higher turn-on voltage, and lower ideality factor compared to the GO/p-Si-based devices. The transport mechanism in the photodetectors can be explained in terms of space-charge-limited conduction and the tunneling of charge carriers through the GO layer.