Self-assembled homojunction In₂O₃transparent thin-film transistors

Abstract

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.