Flexible crystalline β-Ga2O3 solar-blind photodetectors

This paper reports the fabrication of beta-Ga2O3 nanomembrane (NM) based flexible photodetectors (PDs) and the investigation of their optoelectrical properties under bending conditions. Flexible beta-Ga2O3 NM PDs exhibited reliable solar-blind photo-detection under bending conditions. Interestingly, a slight shifting in wavelength of the maximum solar-blind photo-current was observed under the bending condition. To investigate the reason for this peak shifting, the optical properties of beta-Ga2O3 NMs under different strain conditions were measured, which revealed changes in the refractive index, extinction coefficient and bandgap of strained beta-Ga2O3 NMs due to the presence of nano-sized cracks in the beta-Ga2O3 NMs. The results of a multiphysics simulation and a density-functional theory calculation for strained beta-Ga2O3 NMs showed that the conduction band minimum and the valence band maximum states were shifted nearly linearly with the applied uniaxial strain, which caused changes in the optical properties of the beta-Ga2O3 NM. We also found that nano-gaps in the beta-Ga2O3 NM play a crucial role in enhancing the photoresponsivity of the beta-Ga2O3 NM PD under bending conditions due to the secondary light absorption caused by reflected light from the nano-gap surfaces. Therefore, this research provides a viable route to realize high-performance flexible photodetectors, which are one of the indispensable components in future flexible sensor systems.