Investigation of the Intrinsic Nature of Organic Semiconductors Using a Metal Contact-Induced Capacitance Study in Organic Metal–Insulator–Semiconductor Capacitors

Whether organic semiconductors, in their pristine form, are inherently intrinsic or involuntarily doped is an open question that is yet to be addressed. In this work, the source of charge carriers within pristine organic semiconductors, processed in a controlled inert ambience, is investigated using organic metal–insulator–metal capacitor (OMISCAP) devices. Top-gate and bottom-gate architecture of OMISCAP devices based on various organic semiconductors along with different combinations of metal–semiconductor junctions are demonstrated. The impact of the metal–semiconductor junction and the semiconductor thickness on the capacitance–voltage (C–V) characteristics of MISCAP devices is studied to ensure the role of contact-induced charge injection into the semiconductor, contrary to involuntary doping as the source of charge. The charge injection from the metal to the semiconductor is found to be the predominant source of charge carriers inside a pristine organic semiconductor rather than inadvertent doping. The findings in this report are further substantiated using TCAD device simulation.