The use of the semiconductor heterojunction channel layer has been explored as a method for improving the performance of metal oxide thin-film transistors (TFTs). The excellent electrical performance and stability of heterojunction TFTs is easy for vacuum-based techniques, but difficult for the solution process. Here, we fabricated In2O3/In2O3:Gd (In2O3/InGdO) heterojunction TFTs using a solution process and compared the electrical properties with single-layer In2O3 TFTs and In2O3:Gd (InGdO) TFTs. The In2O3/InGdO TFT consisted of a highly conductive In2O3 film as the primary transmission layer and a subconductive InGdO film as the buffer layer, and exhibited excellent electrical performance. Furthermore, by altering the Gd dopant concentration, we obtained an optimal In2O3/InGdO TFT with a higher saturation mobility (µ) of 4.34 cm2V-1s-1, a near-zero threshold voltage (Vth), a small off-state current (Ioff) of 1.24×10-9 A, a large on/off current ratio (Ion/Ioff) of 3.18×105, a small subthreshold swing (SS), and an appropriate positive bias stability (PBS). Finally, an aging test was performed after three months, indicating that In2O3/InGdO TFTs enable long-term air stability while retaining a high-mobility optimal switching property. This study suggests that the role of a high-performance In2O3/InGdO heterojunction channel layer fabricated by the solution process in the TFT is underlined, which further explores a broad pathway for the development of high-performance, low-cost, and large-area oxide electronics.
Keywords: TFTs; doping; heterojunction channel layer; mobility; solution process; stability.