Am - Oled With Zno Base Research Of Tft Constant-current Source Device

Organic light emitting diode has become focal points in display area. AMOLED is the mainstream product of OLED. Except for the OLED light devices, the fabrication of TFT and pixel driver circuit are also the research focus of the AMOLED technology. The mobility of ZnO-TFT is higher than that of a-Si TFT. At the same time, ZnO-TFT does not need fabrication of laser processing and series of complex crystallization process. In addition, the forbidden band width of ZnO is3.37eV, and the transparency is more than80%in the visible band of light. It can not only improve the aperture of TFT, but also can be used to fabricate the transparent AMOLED devices. Since the fabrication temperature of ZnO is low, it can be combined with flexible substrate and fabricate flexible AMOLED devices. Therefore, the research of ZnO-TFT has the great significance to the AMOLED. In order to fabricate the dynamite ZnO-TFT, this paper researched fabrication process of ZnO-TFT and TFTs’electrical properties. In the meantime, it studied the design parameter of TFTs’pixels circuit. This thesis consists of the following four parts:(1) Deposited the Al thin films and ZnO thin films by DC reactive magnetron sputtering and RF magnetron sputtering in ITO glasses. Then we researched the effect of sputtering pressure on the Al thin films, the effect of oxygen/argon flow ratio and the substrate temperature on the ZnO thin films.(2) Fabricated the ZnO-TFT. The devices were fabricated on the insulating SiO2grown on a n-Si substrate. The bottom-gate-type ZnO-TFT was fabricated successfully by the magnetron sputtering, photolithography and the other semiconductor technology. The bottom contact used two photolithography, the ZnO thin films were etched by the solution of HCl and H2O which is the proportion of1/5, and the Al thin films were etched by the solution of phosphoric acid. The top contact used the process of lift-off which did not need lithography.(3) The ZnO-TFTs’ electrical properties were studied with the4200-SCS system. We studied the output characteristic curves and transfer characteristic curves, then calculated the on/off ratio, threshold voltage, field-effect mobility and so on. We discussed the effect of the active layer’s thickness on TFTs’electrical properties. Finally, the stability of the devices was analyzed.(4) Researched the design parameters of TFT’s pixel drive circuit. Analyzed the effect of the parameters of the four pipe pixel circuit on the output current by the HSPICE simulation software.