Photo-Detectivity Modulation in Complementary Light-to-Frequency Conversion Circuits via Oxygen Vacancy Controlled Amorphous Indium–Gallium–Zinc Oxide Films

Herein, light-to-frequency conversion circuits (LFCs) using n-type amorphous indium-gallium-zinc oxide thin film transistors (a-IGZO TFTs) and p-type single-walled carbon nanotube (SWNT) TFTs are proposed as circuit level photodetector. The photoresponse of a-IGZO TFTs under visible spectrum is adjusted with control of annealing temperature condition, which is closely related with oxygen vacancy level, validated by X-ray photoelectron spectroscopy (XPS) and band diagrams in the TFTs. With optimized annealing temperature for a-IGZO TFTs, LFCs are successfully demonstrated by photosensitive complementary inverters and their 3-stage ring oscillators with power and wavelength dependency of light. This result is expected to be applicable to the newly conceived internet-of-things (IoT) sensor systems including interactive displays.