Oxygen partial pressure ratio modulated electrical performance of amorphous InGaZnO thin film transistor and inverter

In this work, sputtering route has been pursued for the deposition of amorphous InGaZnO thin films under different oxygen partial pressure ratio (Oppr). The effect of oxygen partial pressure ratio on the microstructure, optical and electrical properties and chemical bonding states of the sputtering-derived amorphous indium-gallium-zinc oxide (α-IGZO) thin films have been investigated by X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and a series of electrical measurements. Measurements based on α-IGZO/SiO2 thin film transistors (TFTs) have shown that oxygen partial pressure ratio can effectively regulate the carrier concentration, the defect trap density in the bulk channel and the interface between the channel and the gate insulator. The appropriate oxygen partial pressure ratio can reduce interface trap density (Nit) and decrease the off-state current (Ioff), which can obviously improve the on/off current ratio (Ion/Ioff) and the stability of the device. In addition, the appropriate oxygen partial pressure ratio increases the overlap of the ns-orbit of metal ions in the film, which is conducive to improve the electronic transport routes and increase the carrier mobility. As a result, the optimized TFTs performance with oxygen partial pressure ratio of 6.3% has been achieved, including a high saturation mobility (μsat) of 9.9 cm2V-1S−1, a large on/off current ratio of 3.5 × 109, a small subthreshold swing (SS) of 0.29 V/decade, a threshold voltage shift of 4 V under positive bias stress for 7200 s, respectively. A resistor loaded inverter was also constructed on α-IGZO/SiO2 TFTs and exhibited full swing characteristics with a high gain of 10.3, which is sufficient to drive the next stage component in a logic circuit. All the experimental results have indicated that the sputtering-derived α-IGZO thin films have potential application in large-area all-oxide flexible electronics.