Investigations of the effects of electrode geometry and mechanical stress on Antimony doped Zinc Oxide nanostructures based MSM UV photodetectors fabricated on flexible substrates

Abstract In this study, the fabrication and structural characterization of Antimony (Sb) doped Zinc Oxide (ZnO) based interdigitated Metal-Semiconductor-Metal (MSM) Ultraviolet (UV) photodetectors are reported. Sb doped p-ZnO nanostructures were grown using the sol-gel and hydrothermal methods on flexible ITO/PET substrates. Aluminium (Al) interdigitated contacts of thickness 20 nm, were deposited using the thermal evaporation technique to realise planar MSM structures. The structural morphology and element analysis of the as-prepared samples were studied using XRD, FESEM and EDS methods. At an applied magnetic field of 1 T, the Hall measurements revealed that the device had a resistivity of 2.0697 × 10 −3 Ω·cm, a hole mobility of 1922 m 2 /(V·s), and hole concentration of 0.1571 × 10 19 cm −3 . The optoelectrical characterization (without and with 365 nm of UV light) was performed on the MSM photodetectors with different finger electrode spacing i.e. gap sizes (0.1 cm, 0.2 cm and 0.3 cm). The results show that the device with finger spacing of 0.1 cm exhibited the maximum photocurrent. The responsivity and external-quantum-efficiency were calculated as 3.797 A/W and 1292% respectively. The flexible device was subjected to mechanical stress, and the dark current and photocurrent were measured for various bending/ convex arc angles (29.98⁰, 48.72⁰, 64.96⁰ and 97.45⁰). It was observed that the dark current and photocurrent reduce with the increase in bending angles. The current values were reproducible even with repeated flexing and relaxing of the device. This proved that the adhesion of the active layer of Sb doped p-ZnO to the ITO/PET substrate is good, which makes it a good device.