Trap studies in organic semiconductors.
Koh, Thong Boon.
Date of Issue2008
School of Materials Science and Engineering
Organic field-effect transistors (OFETs) are receiving significant attention because of their potential in large area electronics’ applications. Examples of applications are driving circuits for flat panel displays and low-cost applications likes radio frequency identification tags (RFID). In recent years, extensive research has been directed towards p-channel OFETs. The mobility reported for OFETs has exceeded 1cm2/V s which is comparable to those of amorphous silicon. However, the role of semiconductor-dielectric interfacial interactions and particularly its influence on electronic transport is poorly understood. This report presents a systematic study comprising multilayered dielectrics and thermally evaporated Pentacene as the p-channel semiconducting material. In this investigation, sol-gel dielectrics were studied as a possible substitution for the thermally grown SiO2 dielectric layer. Electrical characterization was carried out on Pentacene OFETs with silicon dioxide gate dielectric and silicon dioxide, sol-gel stack gate dielectric. This helped in understanding the transport properties of the Pentacene OFET and the effect of using a novel high k solution processed inorganic gate dielectric. Trap studies for p-type pentacene transistors with and without sol-gel dielectric were also conducted. These studies helped determine whether the improved device performance of sol-gel based devices was related to the dielectric properties. Results presented herein indicate that the improved device mobility is attributable to semiconductor morphology as well as the reduced trap densities at the semiconductor-dielectric interface.