Transferable Ga2O3 Membrane for Vertical and Flexible Electronics via One-Step Exfoliation

Transferable Ga2O3 thin film membrane is desirable for vertical and flexible solar-blind photonics and high-power electronics applications. However, Ga2O3 epitaxially grown on rigid substrates such as sapphire, Si, and SiC hinders its exfoliation due to the strong covalent bond between Ga2O3 and substrates, determining its lateral device configuration and also hardly reaching the ever-increasing demand for wearable and foldable applications. Mica substrate, which has an atomic-level flat surface and high-temperature tolerance, could be a good candidate for the van der Waals (vdW) epitaxy of crystalline Ga2O3 membrane. Beyond that, benefiting from the weak vdW bond between Ga2O3 and mica substrate, in this work, the Ga2O3 membrane is exfoliated and transferred to arbitrary flexible and adhesive tape, allowing for the vertical and flexible electronic configuration. This straightforward exfoliation method is verified to be consistent and reproducible by the transfer and characterization of thick (∼380 nm)/thin (∼95 nm) κ-phase Ga2O3 and conductive n-type β-Ga2O3. Vertical photodetectors are fabricated based on the exfoliated Ga2O3 membrane, denoting the peak response at ∼250 nm. Through the integration of Ti/Au Ohmic contact and Ni/Ag Schottky contact electrode, the vertical photodetector exhibits self-powered photodetection behavior with a responsivity of 17 mA/W under zero bias. The vdW-bond-assisted exfoliation of the Ga2O3 membrane demonstrated here could provide enormous opportunities in the pursuit of vertical and flexible Ga2O3 electronics.