During the past decade, 2D (two-dimensional) materials have attracted enormous attention from various scientific communities ranging from chemists and physicists to material scientists and device engineers. The rise of the 2D materials began in 2004 with the work on graphene done at Manchester University and Georgia Tech. Particularly the observed high carrier mobilities raised early expectations that graphene could be a perfect electronic material. It soon became clear, however, that due its zero bandgap graphene is not suitable for most electronic devices, in particular transistors. On the other hand, researchers have extended their work to 2D materials beyond graphene and the number of 2D materials under investigation is continuously rising. Many of them possess sizeable bandgaps and therefore are considered to be useful for transistors. Indeed, the progress in the field of 2D transistors has been rapid and experimental MOSFETs using semiconducting 2D channel materials have been reported by many groups. A recent achievement was the demonstration of a well-performing 1-nm gate MoS2 MOSFET in 2016. On the other hand, and in spite of the progress in the field, the debate on the real prospects of the 2D materials for future electronics is still controversial.
In the present lecture, the most important classes of 2D materials are introduced and the potential of 2D transistors is assessed as realistically as possible. To this end, two material properties – bandgap and mobility – are examined in detail and the mobility-bandgap tradeoff is discussed. The state of the art of 2D transistors is reviewed by summarizing relevant results of leading groups in the field, presenting examples of the lecturer's own work on 2D electronics, and comparing the performance of 2D transistors to that of competing conventional transistors. Based on these considerations, a balanced view of both the pros and cons of 2D transistors is provided and their potential in both the More Moore (digital CMOS) and the More Than Moore domains of semiconductor electronics is discussed. It is shown that due to the rather conservative CMOS scaling scenario of the 2015 ITRS (compared to the more aggressive scenarios of the previous ITRS editions) it will be difficult for 2D materials to make inroads into mainstream CMOS. However, due to their specific properties (for example, 2D materials are bendable and stretchable) they may enable entirely new applications in the More Than Moore domain.
Frank Schwierz received the Dr.-Ing. and Dr. habil. degrees from Technische Universität (TU) Ilmenau, Germany, in 1986 and 2003, respectively. Presently he serves as Privatdozent at TU Ilmenau and is Head of the RF & Nano Device Research Group. His research interests include semiconductor device physics, novel device and material concepts for future transistor generations, and high-performance radio frequency transistors. At present he is particularly interested in two-dimensional electronic materials.
Dr. Schwierz is conducting research projects funded by the European Community, German government agencies, and the industry. Together with partners from academia and industry he was involved in the development of the fastest Si-based transistors worldwide in the late 1990s, of Europe's smallest MOSFETs in the early 2000s, as well as of the fastest GaN HEMTs on Si and the fastest GaN tri-gate HEMTs worldwide in the 2010s. His recent work on two-dimensional materials made a major contribution to the current understanding of the merits and drawbacks of graphene transistors.
Dr. Schwierz has published more than 260 journal and conference papers including 40 invited papers. He is author of the books Modern Microwave Transistors – Theory, Design, and Performance (J. Wiley & Sons 2003) and Nanometer CMOS (Pan Stanford Publishing 2010) and editor of the book Two-Dimensional Electronics – Prospects and Challenges (MDPI 2016).
Dr. Schwierz is Senior Member of the IEEE. He serves as a Distinguished Lecturer of the IEEE Electron Devices Society and as an editor of the IEEE Transactions on Electron Devices. Moreover, he is one of the key contributors to the Emerging Research Devices Technology Working Groups of the 2013 and 2015 ITRS editions.