Investigation On MgInZnO Transparent Oxide Thin Film Transistors

With the development of display technology, ZnO based transparent thin film transistors (TFT) have been gone into production. Compared to the Poly-ZnO TFT, amorphous ZnO based film doesn’t have grain boundary, thus has better uniformity of the performance. The fabricated TFTs have higher mobility, higher transmittance and better stability. MgInZnO (MIZO) is a new kind of transparent oxide film by doping Mg and In into the ZnO film. The effect of Mg is to suppress the carriers and lower the leakage. In this work, we focus on the fabrication of MIZO films and MIZO TFTs, and then systematically study their properties.In this work, we use the Sol-gel method to fabricate MIZO films. By changing the doping of Mg, the crystalline and transmittance of MIZO films are studied. The fabricated MIZO film is amorphous with excellent transparence. TG-DTA shows that the reaction temperature of MIZO films is above400℃We then fabricate the TFTs using the fabricated MIZO films. It is found that the5%Mg content MIZO TFT shows the best property. The MIZO/Pt Schottky junction made by5%MIZO film and Pt film has the Schottky barrier height of about0.79eV. The properties of the TFT were, the mobility0.064cm2V-1s-1, subthreshold swing (SS)2.93V/dec, threshold voltage5.17V, on/off ratio104. Compared to the normal ohmic contact TFT, the Schottky contact TFT has lower saturation voltage. It can be used to lower the power dissipation.Finally, we studied the degradation of the TFTs and tried to change the process parameter to improve the degradation. It is found that our TFT degraded after storing in the air for one month. It may be caused by the adsorption of water. The restoration of degradation was carried out by annealing. The on/off ratio then returned to103from10. We also investigate the effect of the thickness of the active layer on the TFT properties. Different from the reported paper, we found the thickness of the active layer not only effect the mobility, SS, threshold voltage, on/off ratio, but also effect the saturation voltage of the TFT. The duration and heat resistance of the TFT were also measured.