Stabilized h-BN release layer on PVD-AlN/sapphire template for high-performance GaN-based flexible weak-light photodetectors

Layered hexagonal boron nitride (h-BN) enables the release and transfer of III-nitride epilayers toward flexible electronics, but its insufficient interfacial adhesion to the substrate would limit its compatibility with conventional fabrication processes. Here, based on a sapphire substrate coated with an AlN layer that has the same hexagonal structure as h-BN, the bonding strength of the h-BN/AlN/sapphire structure is significantly enhanced to withstand standard fabrication processes. Meanwhile, epitaxial h-BN on physical vapor deposition-AlN/sapphire sustains its layered structure with releasable properties for device peeling-off and transferring. As such, the h-BN/AlN/sapphire template enables the subsequent growth, fabrication, and wafer-scale transfer of GaN photodetectors (PDs) to flexible substrates. The obtained flexible PDs feature responsivity over 20 A/W with reliable photo-to-dark current ratios under a weak incident light intensity of 23 nW/cm2, even with large bending deformation. This work provides an effective strategy to achieve process compatibility and transferability of III-nitride heterostructures toward large-scale high-performance GaN-based flexible electronics.