High mobility short-channel p-type organic transistors with reduced gold content and completely gold-free source/drain bottom contacts

Pure gold layers are traditionally used for the fabrication of source/drain bottom contacts of high performance short channel pentacene transistors. In this work, these layers are successfully replaced by low cost metallic bilayers, consisting of a thick aluminum layer with a good electrical conductivity covered by a thin noble metal layer (gold or palladium) providing good charge injection into the organic semiconductor. Corresponding pentacene transistors with 5 μm channel length achieve saturation mobilities in the range of 0.4–0.5 cm2/(V s), comparable to those of reference pentacene transistors based on 30 nm thick pure gold bottom contacts, but for a metal cost down to 5% of that of the reference transistors.

Graphical abstractPure gold layers of traditional source/drain bottom contacts of high performance short channel pentacene transistors are successfully replaced by low cost metallic bilayers, consisting of a thick aluminum layer covered by a thin noble metal layer (gold or palladium). Corresponding pentacene transistors with 5 μm channel length achieve saturation mobilities comparable to those of transistors based on 30 nm thick pure gold bottom contacts (0.4-0.5 cm2/(Vs)), but for a metal cost down to 5% of that of the reference transistors.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Short channel pentacene transistors with metallic bilayer S/D bottom contacts. ► S/D bottom contacts of 5 nm thin gold or palladium on 25 nm thin aluminum. ► Large pentacene grains at the bottom contact/dielectric interface. ► Hole transport saturation mobilities above 0.4 cm2/(V s) for 5 μm short channels. ► S/D bottom contact metal costs decreased down to 5% of the reference transistor.