¡@¡@Because of the poly-si thin film transistor have the advantage of high mobility, it can improve the analysis for the flat plan display. Using the above advantage can combine the integrated circuit as control IC and memory on the small panel to reduce the number between the switch circuits and the outside contacts. These precise circuits must be considering the photo current¡Bthermal effects and the parasitical capacitance more due to the influence of these precise circuits is more serious than the switch circuits. In my thesis, the research of the electrical characteristics of the newest excimer laser crystallize coplane poly-si thin film transistors ,and using the device length with width is 128um/6um and 128um/16um can be extracted that the environment of the facing illumination have the photo-leakage current than none illumination about four orders, and the photo-leakage current is not consider with any gate voltage. ¡@¡@With the discussion of the capacitance, the main point of my researches is to change different conditions to extract the gate to source capacitance (Cgs). In addition, the slight carriers may effect the devices with the high mobility system on panel (SOP) technology error, the temperature must be considered. ¡@¡@We find the mobility is bigger at the environment of the temperature is 300K than the environment of the temperature is 100K when the device work in the linear region and the on current is lower at the environment of the temperature is 300K than the environment of the temperature is 100K when the device work in the saturation region. Using some references and some models as the concepts can analysis some phenomenons I refer to above.

Since the traditional CRT(Cathode Ray Tube) replaced by FPD(Flat Panel Display), e.g. LCD¡BOLED¡BPDP, FPD industry is regarded as the important one of global industry following Semi-conductor industry. The main stream of Large-Area Displays is TFT-LCD(Thin Film Transistor-Liquid Crystal Display) and it¡¦s applied a-Si:H TFT (the hydrogenated Amorphous Silicon Thin Film Transistor) as pixel-switch device on LCD. In a-Si:H TFT Cell process, the active region material(a-Si:H) with higher Photoconductivity results into higher off-state current under light illumination and that causes color performance discrepancy as incomplete On/Off operation of pixel-switch devices. As long as the introduction of F into a-Si:H modify the density of states in the gap of a-Si:H(:F), that may result the shift of the Fermi level toward the valence band edge and The density-of-states increasing. It¡¦s effective to decrease the photo leakage current. Due to electro-optical properties of liquid crystal(LC), to drive Pixel-switch device in TFT-LCD shall force On/Off voltage to change Twist Angle of LC is corresponding to have Stress on TFT device. According to DC Stress experiment results, it¡¦s found TFT device with SiF4 dopant can reach better reliability. This issue is aimed to research the photo leakage current variation of a-Si:H TFT at low temperature and ON/Off state effect by stress on TFT device.