Dept. of Electrical Engineering
Oregon Graduate Center
The n- and p-channel field effect transistors have been fabricated in as-deposited and grain boundary passivated polysilicon thin films. The performance of the thin film transistors (TFT's) is characterized and compared for different process conditions. The major cause for the degradation of subthreshold behavior and for the anomalous leakage current in these devices is the presence of the deep level trap sites in grain boundaries. The I-V characteristics are modeled in correlation with the polysilicon material properties, from a unified point of view. A concept of "effective doping" resulting from trapped carriers in grain boundaries is introduced to describe the electrostatics involved therein. The theoretically predicted results are compared with the experimental data and are shown to be in satisfactory agreement. The limitations of the theory are also discussed.
Qian, Feng, "Thin film transistors in polysilicon" (1988). Scholar Archive. 259.