Prof. Siegfried Selberherr, TUWien
Professor Siegfried Selberherr was born in Klosterneuburg, Austria, in 1955. He received the degree of Diplomingenieur in electrical engineering and the doctoral degree in technical sciences from the Technische Universität Wien in 1978 and 1981, respectively. Dr. Selberherr has been holding the venia docendi on computer-aided design since 1984. Since 1988, he has been the Chair Professor of the Institut für Mikroelektronik. From 1998 to 2005, he served as Dean of the Fakultät für Elektrotechnik und Informationstechnik. Prof. Selberherr published more than 400 papers in journals and books. He and his research teams achieved more than 1200 articles in conference proceedings of which more than 200 have been with an invited talk. Prof. Selberherr authored three books and co-edited more than 45 volumes, and he supervised, so far, more than 100 dissertations. His current research interests are modeling and simulation of problems for microelectronics engineering. Prof. Selberherr is a Fellow of the IEEE (1993), a Fellow of the European Academy of Sciences and Arts (2004), a Fellow of the Academia Europaea (2013), and a Fellow of the Asia-Pacific Artificial Intelligence Association (2021).
About Electron Transport and Spin Control in Semiconductor Devices
As the scaling of CMOS-based technology displays signs of an imminent saturation, an introduction of novel non-conventional computational degrees of freedom to sustain the path of energy efficient computing at reduced costs becomes paramount. Employing the second intrinsic electron characteristics – the electron spin – offers additional functionality to electron devices. Apart from forming a qubit, the electron spin is promising for digital applications. We discuss recent advances in spin-based switches: SpinFETs and SpinMOSFETs, as well as nonvolatile CMOS-compatible spin-transfer torque and the spin-orbit torque magnetoresistive random access memories. A modeling approach based on an appropriate extension of the spin and charge transport equations to complex layered structures including tunnel barriers is introduced. As an example, the magnetization dynamics in ultra-scaled MRAM cells is evaluated.
Dr. Farzan Gity, Tyndall National Insitute
Dr. Farzan Gity is a Principal Investigator (PI) and a senior staff researcher at Tyndall National Institute, University College Cork (UCC). In addition to Irish Research Council fellowship, he was the PI of the EU-H2020 SaSHa project at Tyndall. Dr. Gity has also received the Science Foundation Ireland Technology Innovation and Development Award for integrating dissimilar materials for advanced nanoelectronic applications. He is the PI of the EU FET-OPEN INTERFAST project at Tyndall on developing novel spin-based devices. In 2019, Dr Gity has been awarded UCC’s Early Stage Researcher of the Year Award. Dr Gity’s activities involve Emerging Materials and Devices for future nanoelectronics and spintronics applications, including nanofabrication, characterisation and simulations of materials and devices based on two-dimensional materials. He has more than 6 years of collaborative research projects with major semiconductor industries such as Intel.
Mono-material TMD-based heterostructures for nanoelectronics applications
Transition metal dichalcogenide (TMD) based heterostructures can be formed by interfacing two different TMDs through vertical stacking in which these TMDs are interacting through weak van der Waals (vdW) forces, to circumvent the conventional lattice-mismatch problem. Heterostructures of two dissimilar TMDs can be used in device structures with atomically sharp and clean interfaces. TMD-based heterostructures allow for exploring new physics and device architectures by utilising different strategies, such as combining different TMDs, various crystallographic alignment and stacking sequence. Combining monolayers of different TMDs in vertical and lateral geometry allows for manipulating the electrical and optical properties of the heterostructure-based devices.
Molybdenum disulfide (MoS2) is the most studied TMD with a wide variety of applications such as field-effect transistors (FETs), light harvesting devices, chemical sensors, photocatalysts, and flexible electronics. Bulk MoS2 is semiconducting with an indirect bandgap of 1.2 eV, whereas monolayer MoS2 is a direct gap material with a bandgap of 1.8 eV, where the conduction band minimum and the valence band maximum are located at the K-point. Tungsten disulfide (WS2) possesses similar crystal structure as of MoS2 where monolayer WS2 is also direct semiconductor with bandgap of 1.97 eV. Both electron and hole effective masses of WS2 are smaller than that of MoS2. AA’ stacking of monolayer MoS2 and WS2 creates an indirect bandgap material with larger contribution of WS2 valance and MoS2 conduction states. This is consistent with the scanning tunnelling spectroscopy (STS) measurements of MoS2/WS2 heterostructures.
Dr. Gerhard Klimeck, Purdue University
Dr. Gerhard Klimeck is a Professor of Electrical and Computer Engineering at Purdue University; Director of the Network for Computational Nanotechnology; Reilly Director of the Center for Predictive Materials and Devices. He helped to create nanoHUB.org, the largest virtual nanotechnology user facility serving over 2.0 million global users, annually. Dr. Klimeck is a fellow of the Institute of Physics (IOP), the American Physical Society (APS), the Institute of Electrical and Electronics Engineers (IEEE), the American Association for the Advancement of Science (AAAS), and the German Humboldt Foundation. He has published over 525 printed scientific articles; he has been recognized for his co-invention of a single-atom transistor, quantum mechanical modeling theory, and simulation tools. His NEMO5 software has been used since 2015 at Intel to design nano-scaled design transistors. The nanoHUB team was recently recognized by a top 100 by R&D award – Making simulation and data pervasive.
Semiconductor workforce development through immersive simulations on nanoHUB.org
Over 160,000 nanoHUB users have run over 7 million simulations in Apps mostly focused on semiconductor devices and materials modeling. nanoHUB created nano-Apps before Apple created Apps for the iPhone and made scientific codes usable for a much larger user group. Most scientific tools strive to be comprehensive in solving “any” simulation problem in a specific problem range. That comprehensiveness limits the use to experts, who require extensive training. nanoHUB has instead focused on delivering a spectrum of Apps (over 700 now) that individually have a limited capability focused on a PN-junction, MOSFET, or nanowire while the underlying tool could of course solve a much wider set of problems. We assembled some of these Apps that are essential for specific courses into small sets such as ABACUS (crystals, bandstructure, drift-diffusion, pn-junctions, BJTs, MOScaps, MOSFETs). The usability results are stunning. Our user analytics prove that over half of the simulation users participate in structured education through homework/project assignments. We can identify classroom sizes and detailed tool usage. We can begin to build mind-maps of design explorations and assess depth of explorations for individuals and classes. While parts of academia struggled to innovate curricula, we have measured the median first-time App insertion into a class to be less than six months. Over 180 institutions have utilized nanoHUB in their curriculum innovation in over 3,600 classes. 2 million nanoHUB visitors explore lectures and tutorials annually. With such a community presence we believe nanoHUB is the platform of choice to deliver online modeling, simulation, virtual environments, and lectures for the US initiative on workforce development. This presentation will overview some of the nanoHUB impact metrics and turn towards a tool recitation session. In the recitation a brief overview of ABACUS will be given and the audience may request other tool demonstrations or exploration.
Dr. Raphaël J. Prentki, Nanoacademic Technologies Inc
Raphaël J. Prentki obtained his Ph.D. in Physics from McGill University in 2021. His doctoral research focused on charge transport in low-power nanoelectronic devices, notably tunnel field-effect transistors (FETs), negative-capacitance FETs, and cold-source FETs. He studied these emerging systems using both analytical and computational methods of condensed matter and statistical physics, such as the effective mass approximation, the Landauer–Büttiker formalism, the tight-binding model, density functional theory, and the nonequilibrium Green’s function formalism. He joined Nanoacademic Technologies in 2022; he is currently a research scientist and software developer for QTCAD, Nanoacademic Technologies’ newest modeling tool for quantum technologies.
Tunneling leakage in ultrashort-channel MOSFETs—From atomistics to continuum modeling
The channel lengths of some transistors are now nearing the nanometer, making these devices prone to direct source-to-drain tunneling (DSDT), a leakage mechanism commonly considered to set the end of Moore’s law. In a MOSFET, the probability for a charge carrier to undergo DSDT decays exponentially with channel length, source depletion length, and drain depletion length. Bound-charge engineering (BCE) is a recently introduced scheme where the depletion lengths of transistors can be controlled through effective doping by surface bound charges residing on the interface between a semiconductor and an adjacent oxide. In this work, BCE is applied to reduce DSDT leakage current down to acceptable levels in MOSFETs with channels as short as 1.5 nm; the higher the oxide permittivity, the lower the DSDT leakage. As vehicles for this study, we consider n-type gate-all-around MOSFETs with (A) a 2-nm-wide silicon nanowire (NW) channel and (B) a silicon nanosheet (NS) channel. The silicon NW devices are modeled via state-of-the-art atomistic quantum transport simulations based on the nonequilibrium Green’s function (NEGF) formalism and the tight-binding (TB) model, a simulation paradigm currently under development within our first-principles quantum transport software NanoDCAL+ which properly accounts for the atomistic effects, quantum confinement, and nonequilibrium quantum transport phenomena relevant in ultrascaled devices. On the other hand, the silicon NS devices, which are physically larger, are simulated within continuum models after calibration against NEGF–TB data. Specifically, we use the new NEGF–k·p feature under development within the QTCAD software suite (Quantum-Technology Computer-Aided Design), our finite-element-based quantum hardware modelling tool. It is found that short-channel device with high-permittivity oxides exhibit temperature-dependent DSDT, thereby maintaining their subthreshold swing at a value close to the thermal limit of 60 mV/dec at room temperature. BCE may thus pave a way toward ultrascaled MOSFETs. This work highlights the need for simulation platforms combining ab initio simulation tools, which can account for atomistic and quantum effects, with continuum models describing quantum transport at a mesoscopic scale, at which devices are too large to be described purely from first principles but small enough for tunneling to be significant.