Strain-engineered piezo-phototronic interface modulation in flexible GaN/monolayer MoS₂ heterostructures

A flexible, strain-mediated, and photo-responsive device based on a heterostructure comprising a chemical vapor deposition (CVD)-grown MoS₂ monolayer and metal-organic chemical vapor deposition (MOCVD)-grown GaN films is fabricated. By integrating the distinct piezo-phototronic properties of GaN with the excellent carrier transport characteristics of MoS₂, the device exhibits a synergistic response to both mechanical strain and optical excitation. Under compressive and tensile strain, piezo-polarization charges generated in the GaN layer effectively modulate interfacial charge transport at the MoS₂ monolayer, leading to significantly enhanced sensing performance. The device achieves ultrahigh gauge factors of 2224 and 3349 at a compressive strain of -0.25% under halogen and UV illumination, respectively, corresponding to ~11.1 and ~11.7 times higher sensitivity than standard metallic stain gauges. Furthermore, it demonstrates rapid electro-opto-mechanical responses, detecting halogen and UV irradiation with response and recovery times of 186/84 ms and 83/53 ms, respectively, under -0.25% compressive strain. These results reveal strong coupling between strain-induced polarization and photoexcited carrier dynamics at the nanoscale interface. This work provides new insights into strain-engineered interfacial charge modulation in low-dimensional heterostructures and establishes a promising platform for multifunctional, self-powered, ultra-sensitive and active flexible optoelectronics.