Bias stress in pentacene transistors measured by four probe transistor structures

This paper deals with operational lifetime measurements of organic field-effect transistors. The organic semiconductor under study is pentacene. We apply DC stress conditions on these structures, and monitor the output characteristics of the TFTs during stress as well as during recovery after stress. The transistor structures have been modified to incorporate two voltage-measurement probes in the channel in addition to the source and drain contacts. This results in a 4-probe configuration, that allows us to measure the voltage drop in the intrinsic transistor channel separately from the voltage drop over the source and the drain contact regions. This phenomenological study is a first step towards a comprehensive model for degradation of bias stress in organic field-effect transistors.