Performance Of Oxide Thin-film Transistors Research Articles

The Enhanced Performance of Oxide Thin-Film Transistors Fabricated by a Two-Step Deposition Pressure Process.

It is usually difficult to realize high mobility together with a low threshold voltage and good stability for amorphous oxide thin-film transistors (TFTs). In addition, a low fabrication temperature is preferred in terms of enhancing compatibility with the back end of line of the device. In this study, α-IGZO TFTs were prepared by high-power impulse magnetron sputtering (HiPIMS) at room temperature. The channel was prepared under a two-step deposition pressure process to modulate its electrical properties. X-ray photoelectron spectra revealed that the front-channel has a lower Ga content and a higher oxygen vacancy concentration than the back-channel. This process has the advantage of balancing high mobility and a low threshold voltage of the TFT when compared with a conventional homogeneous channel. It also has a simpler fabrication process than that of a dual active layer comprising heterogeneous materials. The HiPIMS process has the advantage of being a low temperature process for oxide TFTs.

Self-assembled monolayers enhance the performance of oxide thin-film transistors

Self-assembled monolayers enhance the performance of oxide thin-film transistors

The role of solution-processed high-κ gate dielectrics in electrical performance of oxide thin-film transistors

We developed a simple and environmentally friendly spin-coating method for high-κ dielectrics (AlOx, ZrOx, YOx and TiOx). These materials were used as gate dielectrics for solution-processed nanocrystalline In2O3 or amorphous InZnO TFTs with a maximum processing temperature of 300 °C. The role of high-κ dielectrics in device performance was systematically studied. Among the high-κ dielectrics, the AlOx-based devices showed the best performance with mobilities of 21.7 cm2 V−1 s−1 in an In2O3 TFT and 11.6 cm2 V−1 s−1 in an InZnO TFT with the on/off current ratio exceeding 106. Furthermore, the devices exhibited ultra-low operating voltages (<3 V) and negligible hysteresis. A comprehensive study suggests that the high performance of the AlOx-based devices could be attributed to the smooth dielectric/semiconductor interface and the low interface trap density besides its good insulating properties. Therefore, the solution-processed AlOx can be used as a promising high-κ dielectric for low cost, low voltage, high-performance oxide electronic devices.

Effect of source/drain preparation on the performance of oxide thin-film transistors

Indium-zinc-oxide thin-film transistors (IZO-TFTs) are prepared with the multilayer structure of molybdenum-aluminum-molybdenum (Mo/Al/Mo) as the source/drain (S/D) electrode. Experiment demonstrates that the sputtering power of Mo (bottom layer of Mo/Al/Mo S/D) influences the performance of TFTs significantly. As the sputtering power increases, the Von runs negative shift, and the device uniformity degrades. XPS depth profile shows that the diffusion at the interface (IZO/Mo) occurs seriously. By decreasing the sputtering power, the diffusion can be suppressed and the devices are shown in normal off state (Von ～ 0.5 V, enhanced mode), with higher mobility (～ 13 cm2·V-1·s-1) and improved uniformity.

Phosphorus Doping Effect in a Zinc Oxide Channel Layer to Improve the Performance of Oxide Thin-Film Transistors

In this study, we fabricated phosphorus-doped zinc oxide-based thin-film transistors (TFTs) using direct current (DC) magnetron sputtering at a relatively low temperature of 100°C. To improve the TFT device performance, including field-effect mobility and bias stress stability, phosphorus dopants were employed to suppress the generation of intrinsic defects in the ZnO-based semiconductor. The positive and negative bias stress stabilities were dramatically improved by introducing the phosphorus dopants, which could prevent turn-on voltage (VON) shift in the TFTs caused by charge trapping within the active channel layer. The study showed that phosphorus doping in ZnO was an effective method to control the electrical properties of the active channel layers and improve the bias stress stability of oxide-based TFTs.