Self-Supported Flexible α-Ga₂O₃ Thin Films Enabled by Nanopillar-Integrated Sacrificial Layers

α-Ga₂O₃, known for its ultrawide bandgap and high breakdown electric field, has attracted significant attention in power electronics and solar-blind photodetectors. However, the rigid and insulating nature of sapphire substrates restricts the development of flexible α-Ga₂O₃-based devices, vertical power devices, and high-power electronics. Here, self-supported flexible α-Ga₂O₃ thin films were prepared by a Bridge Pier-like structure. In this structure, highly vertical and dispersion-controlled α-Ga₂O₃ nanopillar arrays, an α-Fe₂O₃ array-type sacrificial layer, and high-quality α-Ga₂O₃ epitaxial films were sequentially grown on sapphire substrates by an economical mist chemical vapor deposition (mist-CVD) technique. The flow channels created by the array-type sacrificial layer significantly enhanced etchant flow, enabling the rapid detachment of freestanding 3-μm-thick α-Ga₂O₃ flexible films in just 20 min─a nearly 10-fold increase in detachment efficiency compared to conventional sacrificial layer designs. The freestanding α-Ga₂O₃ thin films were used to fabricate flexible solar-blind photodetectors that, under 254 nm ultraviolet illumination, achieved an on/off ratio of 0.57 × 10³ and a detectivity of 3.18 × 10¹⁰ Jones, while also exhibiting exceptional mechanical flexibility and optoelectronic stability with no degradation observed after 1000 bending cycles. This work provides a pathway for the fabrication of α-Ga₂O₃ flexible devices and freestanding substrates, offering an innovative strategy for the rapid detachment of thin films in heteroepitaxial systems.