Benchmarking contact quality in N-type organic thin film transistors through an improved virtual-source emission-diffusion model

Due to nonideal behavior, current organic thin film transistor technologies lack the proper models for essential characterization and thus suffer from a poorly estimated parameter extraction critical for circuit design and integration. Organic thin film transistors are often plagued by contact resistance, which is often less problematic in inorganic transistors; consequently, common models used for describing inorganic devices do not properly work with organic thin film transistors. In this work, we fabricate poly{[N,N & PRIME;-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5 & PRIME;-(2,2 & PRIME;-bithiophene)} based organic thin film transistors with reduced contact resistance through the introduction of metallic interlayers between the semiconductor and gold contacts. The addition of 10 nm thick manganese interlayer provides optimal organic thin film transistor device performance with the lowest level of contact resistance. Improved organic thin film transistors were characterized using an improved organic virtual-source emission diffusion model, which provides a simple and effective method to extract the critical device parameters. The organic virtual-source emission diffusion model led to nearly perfect prediction using effective gate voltages and a gate dependant contact resistance, providing a significant improvement over common metal-oxide-semiconductor field-effect transistor models such as the Shichman-Hodges model.