Self-assembled homojunction In2O3 transparent thin-film transistors

Homojunction transparent thin-film In₂O₃ transistors were fabricated at room temperature. Self-assembled In₂O₃ source-channel-drain structures were grown by pulsed electron beam deposition using a shadow mask with a 300 µm diameter wire as an obstacle placed at ∼100 µm distance from the substrate for growing the channel region behind it. The film resistivity varies from ∼7 × 10⁸ Ω cm in the channel region to ∼10^-3 Ω cm in the source-drain regions. We explain this fact by the relative depletion of the indium incorporated in the channel region of the film due to the reduced flux of ablated species arriving on the substrate behind the obstacle, leading to a relative enrichment in oxygen compared to the source and drain regions. The gate insulator is a Y₂O₃ film grown by RF magnetron sputtering. The transistor operates in enhanced mode. The subthreshold swing is ∼0.26 V/decade with an on/off current ratio of 1.5 × 10⁷, and the saturation channel mobility is greater than 45 cm² V^-1 s^-1.