Speaker : Logesh K (EE12D015)
Date : July 3, 2019 (Wednesday)
Time : 3.00 PM
Venue : ESB 244, Seminar Hall
Guide : Dr. Soumya Dutta
Over last two decades, a considerable amount of efforts has been implemented on improvement of OFETs due to their tremendous potential in circuit application, sensing, photo-detection, light emission etc. together with availing the advantages such as low temperature processing, mechanical flexibility, and excellent optical properties. We have demonstrated the technology to fabricate array of OFETs with isolated gate and lithographically patterned source/drain, using poly(3-hexylthiophene) (P3HT) as an organic semiconductor and poly(4-vinylphenol) (PVP), a solution based transparent polymer as gate dielectric. Even though having identical device performance with high yield, leading to one step forward to the feasibility of circuit applications, we need more investigation on their stable device operation. In this seminar, we focus on influence of metal-semiconductor interface on the device performance.
Uncontrolled hysteresis in transfer characteristics is one of the major concerns that causes different drain currents (IDS) for a particular gate voltage (VGS), depending on the direction of voltage sweep. This can result in a serious issue for circuit application as a consequence of threshold voltage shift. In the present study, we investigate the role of metal-semiconductor junction in hysteresis, which eventually becomes more prominent while scaling down the device dimension. Based on the experimental signature and the correlation between contact resistance and hysteresis, we demonstrate the route to reduce/mitigate that issue. To explore the influence of metal-semiconductor contact on field-effect devices, we study organic metal-insulator-semiconductor (MIS) capacitor, which is considered as a model device structure to comprehend the transistor operation. In this context, we discuss about the operation of organic MIS capacitors, concept of unintentional doping, validity of Mott-Schottky relationship, and the role of metal-semiconductor junction in capacitance dispersion with respect to operating frequency. Apart from commercially available organic semiconductors, we also implement in-house synthesized organic semiconductors as active materials for OFETs and explore the chemical tunability of the semiconductors to achieve high charge injection at the metal-semiconductor junction for improved device performance.
All are cordially invited.