High-frequency operation of Organic Permeable Base Transistors Device optimization, compact model development, and benchmark circuits

• Applicants: Ghader Darbandy, Ph.D.; Dr. Hans Kleemann
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 496804567

With a cutoff frequency of 40 MHz, a ring-oscillator stage delay of 11ns, and a driving voltage of <10V, organic permeable base transistors (OPBT) are among the best-performing transistors available for flexible electronics. In contrast to conventional organic thin-film transistors, research on OPBTs and in particular on their dynamic behavior is still at an early stage. Fundamental scaling laws, effects of self-heating and non-quasistatic phenomena are insufficiently understood in these vertical transistor devices impeding the development of compact models which is an important step towards device integration. Additionally, based on a deeper understanding of the device physics, optimizations might be predicted based on compact models allowing to boost the dynamic performance of OPBTs even further.The main objective of this research proposal is to fabricate, characterize, analyze, model, optimize, and design OPBTs and benchmark circuits targeting a cutoff frequency approaching 1 GHz. We will reach this aggressive goal by implementing new semiconductor materials with increased vertical carrier mobility, decreasing contact resistances, minimizing intrinsic and extrinsic parasitic capacitances, and optimizing structural and material properties.We will fabricate optimized OPBTs designed for high-frequency operation based on the developed physical models and minimize parasitic capacitances. In order to boost the dynamic performance of OPBTs to the GHz-range, triclinic rubrene thin-film crystals with a vertical carrier mobility of 10 cm2 V-1 s-1 will be implemented into the novel OPBTs. We will investigate the pinhole formation process in the base electrode and analyze how this process can be fostered. Alternative printing or/and photolithography integration techniques will be explored and employed to advance the integration of OPBTs into complex circuits. These device optimizations will be closely accompanied by the development of a calibrated TCAD simulator for OPBTs. The TCAD simulator will help us to gain a deeper physical understanding of device operation in order to predict further optimization steps, e.g., to minimize parasitic capacitances. In fact, the physical compact modeling bridges the OPBT technology and advanced designs of the integrated circuits representing an essential step towards applications. The physical modeling will be used for predicting the actual device/circuit DC/AC performances and designing optimized devices depending on the desirable circuit’s figures-of-merit (FoM) operating in the ultra-high-frequency regime, determined by the targeted applications. The applicability of the developed compact models for performance evaluation of the OPBTs at circuit level will be verified and proven by benchmark circuits under realistic circuit operation conditions.

• DFG Programme: Research Grants