Fabrication and characteristics of permeable-base organic transistors based on co-evaporated pentacene:Al base

In this letter, fabrication and characteristics of a p-type permeable-base organic transistor are reported. A hole-type organic semiconductor pentacene is used as emitter and collector. The permeable pentacene:Al base is formed by co-evaporating pentacene and Al in vacuum. The device performance has shown to depend on the evaporation rate of pentacene in the pentacene:Al co-evaporation, where the evaporation rate of Al is controlled at 1 nm/s. Controlling the evaporation rate of pentacene at 0.1 nm/s in the pentacene:Al co-evaporation, the device shows the optimal common-base current gain of near 1 and common-emitter current gain of ∼137.

Based on our experiments, the base construction and the pinhole structure (middle, SEM images of the base layers with different pentacene doping level), and consequently, the electrical characteristics (right, the common-base and common-emitter current gain of the transistors with different pentacene doping level) of the studied transistor (left, the device structure) depend on pentacene doping level of the co-evaporated pentacene:Al base.Figure optionsDownload as PowerPoint slideHighlights
► Permeable-base organic transistors based on pentacene:Al base are fabricated.
► Pentacene-doping in Al deposition causes dispersive pinholes within base area.
► Un-uniformity and diameters of the pinholes increase with pentacene-doping level.
► Transistor characteristics depend on pentacene-doping level.