Continued scaling of transistors has forced us to scale the channel thickness of the device to have strong electrostatic control and get rid of the short channel effects. The reduced channel thickness results in the confinement of charge carriers and larger quantization effect. In addition to the scaling, alternative channel materials having better transport properties are also being explored to boost the device performance. The promising options for channel materials in post Si era are Ge, SiGe, III-V and 2D layered semiconductors. The III-V semiconductor materials have lower effective mass and as a consequence lower density of states (DOS). The lower DOS introduces a new capacitance component in gate capacitance in addition to the existing charge centroid and gate oxide capacitance and is called as quantum capacitance. Scaling has also resulted in channel lengths of modern and upcoming devices to be comparable to the mean scattering lengths of the semiconductor material. This causes some of the charge carriers to travel from the source to the drain without any significant scattering. Therefore, the generic principles governing the drift-diffusive framework, i.e. (i) the concept of mobility, and (ii) local field dependent velocity, are no longer valid. This quasi-ballistic transport results in significant deviation from the device behaviour predicted by traditional drift diffusive models. Since different carriers experience different amounts of scattering, modeling such devices is not only interesting but also challenging. In this talk, I will discuss the physics and modelling of different quantum effects and transport in extremely scaled transistors with different channel materials.
Dr. Yogesh Singh Chauhan is an associate professor at Indian Institute of Technology Kanpur (IITK), India. He was with Semiconductor Research & Development Center at IBM Bangalore during 2007 – 2010; Tokyo Institute of Technology in 2010; University of California Berkeley during 2010-2012; and ST Microelectronics during 2003-2004. He is the developer of several industry standard models viz. BSIM-BULK (formerly BSIM6), BSIM-CMG, BSIM-IMG and ASM-HEMT etc. His group is involved in developing compact SPICE models for GaN HEMT, FinFET, Nanosheet/Gate-All-Around FET, FDSOI transistor, Negative Capacitance FET and 2D FET. He is the Editor of IEEE Transactions on Electron Devices and Distinguished Lecturer of the IEEE Electron Devices Society. He is the member of IEEE-EDS Compact Modeling Committee and fellow of Indian National Young Academy of Science (INYAS). He is the founding chairperson of IEEE Electron Devices Society U.P. chapter and Vice-chairperson of IEEE U.P. section. He has published more than 200 papers in international journals and conferences. He received Ramanujan fellowship in 2012, IBM faculty award in 2013 and P. K. Kelkar fellowship in 2015, CNR Rao faculty award, Humboldt fellowship and Swarnajayanti fellowship in 2018. His research interests are characterization, modeling, and simulation of semiconductor devices. He has served in the technical program committees of IEDM, SISPAD, ESSDERC, EDTM, and VLSI Design conferences.