Photosensitive properties of α-IGZO thin-film field-effect transistors

Amorphous indium-gallium-zinc-oxide (α-IGZO) composed of In₂O₃, Ga₂O₃ and ZnO is an n-type semiconductor with a band width of 3.5 eV, and currently it has become a hot research field of field-effect transistors for its properties. In order to investigate its potential application for future photoelectric sensors, by fabricating electrodes with a mask, here we present a bottom-gate/top-contact field-effect transistor with structure of ITO/SiO₂(400 nm)/α-IGZO(50 nm)/Al in which α-IGZO acts as active layer, and its photosensitive properties are characterized. After thermally evaporating Al layer to fabricate drain and source electrodes with a mask, the device is annealed in ambient air at 350°C for an hour, and the α-IGZO-based thin-film field-effect transistor (TFT) shows good transistor characteristics of a mobility of 0.57 cm²/Vs at V_GS=30 V and a threshold voltage of 15.0 V. Under white light illumination with an intensity of 8.1 mW/cm², the device shows obviously enhanced photosensitive properties, its mobility increases to 1.34 cm²/Vs at V_DS=20 V and V_GS=30 V, its threshold voltage reduces to -15.0 V, and its current ratio (K) of photocurrent to current in dark reaches a maximum at V_GS=2.5 V with a responsivity of 1.11 A/W presenting good time-responsive characteristics.