Abstract
In this thesis, we investigate the vertical-type organic thin film transistors (OTFTs). All the devices are fabricated through shadow masks by thermal evaporation. From the current-voltage (I-V) characteristics of thickness-varying Schottky diodes, we conclude that the thick organic layer is unfavorable to current injection though it also provides higher breakdown voltage. We confirm that the thermal-assisted carrier transport mechanism and the thickness-dependent trapping energy levels from the temperature-varying I-V characteristics and Arrhenius plots. The first vertical-type transistor we fabricate is static induction transistor, and it provides a current on/off ratio of 4 and a high current output in the order of milliampere. But the limitation of the shadow mask prohibits us from enhancing its performance. Therefore, we pursue our investigation with a promising vertical-type structure, hot-carrier triode. The devices show transistor-like characteristics which output current can be modulated by demanding different input currents on their thin metal base electrodes. They also exhibit a good current saturation with current gain of 2.38. The mechanism of operation is proposed and examined by the basic electrical measurements.