Improved Detectivity of Flexible a-InGaZnO UV Photodetector via Surface Fluorine Plasma Treatment

Amorphous InGaZnO (a-IGZO) UV photodetectors with a metal-semiconductor-metal structure were fabricated on polyethylene terephthalate (PET) substrates, and the effects of surface fluorine plasma treatment on a-IGZO were investigated. With this treatment, the oxygen vacancies (O
_vac
's) at the a-IGZO surface were effectively passivated, thus reducing the shallow-level donor states and electron traps. Accordingly, the direct and/or trap assisted tunnelings through the metal/a-IGZO Schottky barrier were suppressed, leading to a significant reduction in the dark current. On the other hand, the photo current was nearly unchanged if the treatment time was less than 20 min. It is due to the simultaneous reductions in hole trap and recombination center, both of which are related to the Ovac's at deep levels. As a result, a high detectivity of 4.36 × 10
¹³
Jones was realized with an increase of nearly 10 times. Moreover, a highly uniform trap distribution was achieved, and it could be beneficial to the photoconductive reliability of the device.