Abstract
Recently, new imaging devices that take advantage of the TFT array have been developed in the non-display field. The majority of touch-enabled AMLCDs, active matrix liquid crystal display, are based on resistive, capacitive or inductive touch technology. All these solutions require externally added components or screens, which add cost and reduce optical performance. A photodiode integrated into each pixel of the TFT array, or a photoconductive layer formed on the TFT array. In this device, the electric charge is generated in the photo-detective and is stored in the pixel, depending on the outside of light signals. The charge information is then read out as the imaging data by sequential line-addressing. In consumer application, several types of imaging devices have been reported, for example, the document imager, name card reader, and fingerprint reader. It is well known that a-Si TFTs has a high photocurrent under exposure to visible light. The advantages of the photosensitivity of a- Si TFT is integrated an optical sensor array into the AMLCD display for example for touch location detection by finger, stylus, light pen or laser pointer. So, A good photo sensor should possess low dark-current, high photo- current, high optical gain, high sensitivity and fast response time. In this thesis, we try to use the simulation software to optimize the a-Si TFT device and realize the TFT device. Enhancing the Photo/dark current of a-Si TFT device that is real challenge. We used the simulation software to evaluate the TFT device and verified some physical of TFT parameters. After work- station simulation, we obtained the gradient of channel doping that can enlarge the photo current because of the electronic field. Otherwise, we design several shapes of the TFT devices, like symmetry structure、non-symmetry structure、differential channel width and length of the TFT devices、micro lens array lie on top of the TFT devices. After analysis of these devices by HP 4156, the best result of photo/dark current is about 5 ~ 6 orders. Comparing with the previous papers, the common photo/dark ratio is around 3 orders. In this research, we largely improve the performance of Photo sensors. We believe that the consumer application will be further evolved widely base on this development.