Transparent, Multivalued Transistors Enabled By Area-Selective Optical Doping on Ga-Doped IZTO Thin Films

Multivalued transistors are demonstrated on wafer-scale, sputtered gallium-doped indium-zinc-tin-oxide (Ga-doped IZTO) thin films by area-selective optical doping. Cation elemental doping and ultraviolet (UV) exposure are representative techniques to control the carrier concentrations of metal oxide semiconductors. In this work, both doping techniques are exploited to design a pseudo-heterojunction on a monolithic Ga-doped IZTO thin film to generate multivalued electrical characteristics. The resulting semiconductor channel possessed two distinct work functions (i.e., smaller work function on the UV-exposed area with respect to the masked Ga-doped IZTO area), which resulted in sequential activation with two turn-on voltages under a gate voltage sweep. Consequently, a stable intermediate state is generated for the ternary operation of the devices. This work further demonstrates the fabrication of transparent ternary device arrays by utilizing transparent elements including indium tin oxide (ITO), Ga-doped IZTO, SiO₂, and glass as electrodes, semiconducting channels, dielectric layers, and substrates, respectively.