An analytical solution for contact resistance of staggered organic field-effect transistors

摘要

We have developed analytical models for bias dependent contact resistance (R_c) and output characteristics of staggered organic field-effect transistors (OFETS) based on a bulk resistance-approximated and mobility-modified current-crowding method. Numerical evaluations of R_c and its resistive components show that the bias dependency of the bulk resistance is negligible. Consequently, the properties of the active layer interfaces determine R_c and its characteristics. Effective parameters include a normally constant charge injection barrier at the organic-metal interface (E_b) and a gate induced surface carrier-concentration (P_(So)) at the organic-insulator boundary. The energy barrier pertains to the fabrication process, and its related resistance (r_c) can be determined as the fitting parameter of the theoretical model. However, P_(so) is strongly gate bias dependent and the results of the numerical model indicate that the resulting component (r_(ch)) is dominant and has a considerable effect on R_c and its characteristics. More importantly, P_(so) as the key parameter of the contact resistance is analytically expressible and by using a proposed mobility-modified current-crowding model, the contact resistance can be analytically formulated. Accordingly, the output characteristics of the OFETs in the triode region can be also analytically modeled using the developed relation of Rc.