The Research Of Pentacene Based OTFT Using Al₂O₃as Gate Dielectrics

The interface characteristics between the insulating layer and organicsemiconductor film is playing an important role in the performance of organic thin filmtransistors (OTFTs). So it is necessary to study the interface characteristics andmorphology of organic film for OTFTs. In this paper, we carried out our research onOTFTs from the following three aspects:Firstly, we used ALD technology to develop a thin Al2O3film as high-k insulatinglayer on heavily doped silicon wafers. The Al2O3film was annealed at differenttemperatures, which are0oC,80oC,120oC and160oC, respectively. Then the pentacenefilm was developed on Al2O3film and we obtained four OTFTs which were all bottomgate top contact structure. The results show that annealing technology can improve themorphology of the pentacene film which can enhance the performance of those OTFTs.And the OTFT annealed at160oC annealing was the best one, which can obtain themobility up to0.16cm2/V·s and the threshold voltage down to-1.6V. By studying theorganic semiconductor capacitor and AFM of the pentacene film, it can demonstrate thatthe annealing process improved the quality of the insulating layer which was beneficialto form a good morphology of the pentacene film. At a result, annealing increased thecarriers mobility.Secondly, we prepared four OTFTs,which are different in thickness of pentacenefilm, were20nm,40nm,60nm and80nm, respectively. We found that the OTFTs basedon pentacene has an optional thickness range which was about in35~50nm. The reasonis the process of film growing and the contact resistance.Finally, an attempt was done in researching OTFTs with numerical simulation.After incorporating the contact barrier of pentacene film, mobility of Poole-Frenkelfield-dependence and density of trap state, the simulation fitted precisely with the outputof experiment.