Soft & Smart Materials & Devices Lab

In recent years, oxide semiconductors have superior electrical properties, low thermal budgets, and uniformity across large areas render them essential for advanced electronic technologies. Nevertheless, attaining a mobility exceeding 100 cm2/Vs remains challenging, which positions In2O3 with its large 5s orbital as a promising candidate to overcome this limitation.  Oxide thin-film transistors (TFTs) with high mobility that exceed 100 cm2/V·s and appropriate turn-on voltage (Von) are necessary to drive next-generation displays and memory devices. However, a trade-off relationship exists between mobility and Von, making it difficult to achieve both in the same oxide TFT. In this letter, we propose a buffer layer engineered trench-TFT (T-TFT) as a solution to this trade-off problem. Trench TFT shows a high mobility of 129 cm2/V·s and a suitable Von of −0.4 V. In this trench TFT, the horizontally thick regions of the active layer function as highly conductive current paths, whereas the vertically thin regions serve as effective channels, which result in an on-current boosting effect. The device exhibited a favorable SS of 0.108 V/dec and reasonable Von of −0.68 V. Ga has been widely used as a carrier suppressor in oxide semiconductors; however, research has recently been conducted to replace it with Al, which is cheaper and forms a stronger bond with O. In this study, an InAlZnO (IAZO) semiconductor was deposited using super-cycle PEALD for the first time. AlO (AO), AlZnO (AZO), and InAlO (IAO) as Al doping layers in IAZO are evaluated. Finally, the high-Al IAZO system using AZO successfully showed overall excellent properties including mobility over 10 cm2/Vs, and outstanding stability under 0.1 V, which are greatly improved compared to previously reported IAZO TFTs.  To