Vertical-Type Organic Transistors
In the 1980s, research into organic fi eld-effect transistors (OFETs) was initiated to investigate the characteristics of organic semiconductors, such as fi eld-effect mobility . In recent years, OFETs have been developed for novel
electronic devices such as fl exible displays based on organic light-emitting diodes (OLEDs), electronic papers, radio frequency identity (RF-ID) tags, and biosensors [2-6]. In the intervening quarter-century, fi eld-effect mobility has been increased from 1 × 10-5 [cm2/Vs] to 40 [cm2/Vs] [7-8]. However, conventional OFETs have remaining issues, such as higher operational voltage compared with inorganic transistors, which have prevented the fabrication of practical mobile electronic devices. The low performance of such devices is mainly due to the low-mobility and high-resistivity of organic semiconductors. Many different approaches have been made in an attempt to improve the performance of OFETs, as shown in Figure 10.1.