Synergistic combination of amorphous indium oxide with tantalum pentoxide for efficient electron transport in low-power electronics

Among transparent metal oxide semiconductors, systems based on indium oxide currently deliver the best combination of electronic characteristics and optical transmittance, outperforming even the well-established polycrystalline silicon devices. Indium oxide has the unique property that uniform, amorphous films yield superior electronic properties compared to microcrystalline films; for this reason, Ga and Zn hetero-elements are usually added to disrupt crystallization and result in uniformly disordered films. However, dopants have a general tendency to increase the complexity and decrease the mobility of semiconductors and their addition might well be avoided if high-quality, amorphous In₂O₃ films could be grown without them. In this work, we show that this problem can be resolved by exploiting a synergistic interaction between solution-processed indium oxide (In₂O₃) and underlying tantalum pentoxide (Ta₂O₅) dielectric films. We observed that amorphous Ta₂O₅ inhibits crystallization of In₂O₃ leading to high-quality amorphous thin films with reduced oxygen deficiencies at the semiconductor/dielectric interface. Transparent Ta₂O₅/In₂O₃ TFTs with very low operating voltages were demonstrated with effective field-effect mobilities of up to 23.1 cm² V^-1 s^-1 at only 3 V drain-source voltage (V_DS) using this approach. Additionally, the suppressed carrier density arising from reduced oxygen deficiencies reduced the drain current at 0 V gate bias (I₀) by six orders of magnitude from 0.25 mA to 10.8 nA, compared to a SiO₂ reference device. These results highlight the importance of considering an underlying dielectric layer to maximize device performance.