Influence of Double Channel Layers on the Performance of Nitrogen Doped Indium-zinc-oxide Thin Film Transistors

The nitrogen-doped amorphous indium-zinc-oxide thin film transistors with double channel layers (a-IZO/IZON-TFTs) were fabricated by RF magnetron sputtering of IZO target on the thermal oxidized p-type Si substrate. Influence of the double channel layers on the electrical performance and thermal stability of the devices were investigated. It is found that a-IZO/IZON-TFTs have high field effect mobility of 23.26 cm(2)/(V.s) and more positively shifted threshold voltage than that of a-IZO-TFTs. This is ascribed to the doped nitrogen which can help reduce oxygen vacancy in the channel layer, suppress carrier concentration and make the devices have a better threshold voltage. Meanwhile, employing a-IZO thin film can avoid the sharp drop of field effect mobility and drain on current caused by nitrogen doping on a-IZON layer, leading to promoting I-on/I-off ratio effectively. Besides, according to the transfer characteristics measured at temperatures from 298 K to 423 K, devices with a-IZO/IZON double layers have superior performance and thermal stability to TFTs of single channel layer, which can be ascribed to the protective effect of a-IZON thin film on the channel layers. The doped nitrogen can reduce the adsorption/desorption reaction of oxygen molecules on the back channel layer, leading to a significant improvement on thermal stability of the devices.