ZnO/GZO Multi-channel Layer Thin Film Transistors Using the Effect of 2DEG

Thin-film transistors (TFTs) have been playing an important role in the LCD display industry. The recent trend of TFTs is the transparent pixel, which can be fulfilled by using zinc oxide (ZnO) as the active layer. ZnO is the material with properties of wide bandgap, high mobility, and easy deposition by RF sputtering at room temperature. ut ZnO also has some drawbacks like the low operating current level and the stability problem. We introduce the gallium doped zinc oxide (GZO) as the active layer. GZO does solve the drawbacks of ZnO above but new problems arisen. We have tried many channel thicknesses and gate sizes of ZnO and GZO TFTs in order to find the best structures of each kind of TFTs. We have successfully explained the structure differences of TFTs by use of a model. e have also fabricated the delta-doped TFTs so as to further improving of current level and response time. A model has been showed to explain the operation of devices by forming a 2-dimentional electron gas (2DEG) structure in the channel layer successfully, and the controllable threshold voltage is also proved by varying the composition of the delta-doping layer. The result of our delta-doped TFTs is much better than the previous work in our lab, and is believed to be one of the best ZnO-based TFT performances in the world.