Virtual source emission model leads to improved organic thin film transistor

Electronics based on organic semiconductors have garnered increased attention in recent years because of their potential for lightweight and low-cost roll-to-roll manufacturing on flexible substrates. However, current electrical models are inadequate for capturing non-ideal features of organic thin film transistors (OTFTs), such as contact resistance.

Dallaire et al. designed a series of OTFTs with ranging contact resistances by introducing metallic interlayers between the semiconductor and gold contacts. Guided by a new virtual source emission model, the authors could accurately identify the effect of contact resistance on the resulting electrical performance. This indicated a 10-nanometer-thick interlayer of manganese was ideal to boost the device performance.

The virtual source emission model provided a significant improvement over common metal oxide semiconductor field-effect transistor models.

“We provide a model that demonstrates much greater fit to real actual data than the classical models,” said author Benoit Lessard. “We demonstrate the clear effect of contact resistance on model fitting by providing experimental data for the same system but with different interfacial layers to control the contact resistance.”

Unlike conventional metal oxide semiconductor field-effect transistors, OTFTs often suffer from nonideal performance due to limited charge injection into the device channel. This leads to high contact resistance and poor estimation of charge mobility or threshold voltage, making it almost impossible to design organic circuits or integrate them into actual applications.

The group’s organic virtual source emission diffusion model led to nearly perfect prediction using effective gate voltages and a gate dependent contact resistance.

They aim to continue studying the links between manufacturing, processing and production of organic electronics that have predictable and tunable properties.

Source: “Benchmarking contact quality in N-type organic thin film transistors through an improved virtual-source emission-diffusion model,” by Nicholas Dallaire, Samantha Brixi, Martin Claus, Stefan Blawid, and Benoit H. Lessard, Applied Physics Reviews (2022). The article can be accessed at https://doi.org/10.1063/5.0078907 .