HIGH PERFORMANCE PATTERNED SOURCE ELECTRODE VERTICAL ORGANIC FIELD EFFECT TRANSISTOR

Vertical organic field effect transistor is a growing research topic due to the industry demand for high-performance low-cost thin-film transistors. In vertical transistors the channel length is determined by the semiconductor film thickness. Therefore, it is possible to fabricate a short channel high-performance device in spite of the organic semiconductors’ relative low mobilities. In our design of vertical transistors the gate electrode is located beneath the source electrode and controls the amount of carriers injected from the source electrode to the organic semiconductor. From the semiconductor the carriers swiftly cross the very short channel length towards the drain electrode. We developed a new fabrication processes of n-type and p-type vertical transistors reaching on/off over 10⁵ and current densities above 10mA per cm². Complementary inverters was successfully assembled using those transistors.

Owing to the patterned source electrode technic, the gate is able to induce an efficient potential barrier lowering between the source electrode and the semiconductor. The fabrication process is compatible with large-area and low-cost fabrication. Using simple one step photo-lithography and lift-off process patterned electrode with holes in sizes of 2-20 µm is fabricated. In this process a blocking layer is added on the top of the source electrode in order to reduce off currents for better performances. To achieve high on/off ratio there must be an injection energy barrier between the source and the organic semiconductor. When using gold as source electrode it is possible to fabricate P-type and N-type transistor at the same process just by changing the organic semiconductor casting.