The French Alternative Energies and Atomic Energy Commission (CEA-Liten)
Investigation on Hysteresis and Bias Stress Behavior for low-Voltage Organic Transistor Based on Relaxor-Ferroelectric Polymers
Organic electronic reached a turning point in its development, as mobility and stability of organic semiconductors enable first applications for displays and signage. On the other hand organic transistors have also enabled low-voltage operations owing to new processes paving the way for low-power fully organic electronic circuits. As demonstrated in the literature the low-k/high-k bilayer dielectric could be a promising candidate for printed Organic Field Effect Transistors (OTFTs)1). By introducing a layer of high permittivity relaxor ferroelectric material the gate capacitance is drastically increased thus reducing threshold voltage (Figure 1). However in practical circuit the transistors would be confronted to long electrical stress that may impact their electrical characteristics and thus degrading their functionality. When exposed to Gate Bias Stress as a function time, the threshold voltage of P(VDF-TrFE-CTFE) bilayer structure exhibits a characteristic turn around behavior with amplitude depending on the applied gate voltage during stress (cf Figure 2 b) ). This behavior is very different from the one observed for low-k dielectrics reference transistors, showing a monotonous shift without any gate bias dependency. This feature clearly indicates that, in the high-k material, a specific degradation mechanism occurs as compared to the classical monotonous stress degradation. By carefully studying the bilayer response in a capacitor structure versus the temperature, we were able to determine the Curie temperature and other related phenomenon allowing for a better physical understanding of the structure’s operation. V.Pecunia et al.,«Trap Healing for High-Performance Low-Voltage Polymer Transistors and Solution-Based Analog Amplifiers on Foil», Adv. Mater.,vol.29, no 23, p.1606938,juin_2017
After obtaining two Master’s degree from “Bordeaux Graduate School of Chemistry, Physics and Biology” (ENSCBP, Bordeaux, France) and the University of Bordeaux (France) Alexandre Gaïtis was part of the material research team at FlexEnable (Cambridge, UK) for nine month. In April 2016 he started his PhD in electronic Organic at the CEA-LITEN (Grenoble , France) in partnership with IMPEC-LaHC (Grenoble, France).
Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA) is a French research-and-technology organization with activities in energy, information technology, healthcare, defense and security. CEA-Tech which is one of its divisions, focuses on creating value and innovation through technology transfer to its industrial partners. It operates 8,000-m² of state-of-the-art clean room space on 200mm and 300mm wafer platforms and as well the printed platform called “PICTIC” dedicated to TOLAE activities. The LITEN laboratory is a team of more than 50 persons devoted to printing process development for organic devices (OTFT, OPD, sensors and actuators), ink formulation, organic device modeling and simulation and device characterization and reliability. This department operates the French printing pilot platform PICTIC.