Carbon nanomaterial transistors and circuits

Throughout much of the semiconductor industry’s history, the digital transistor maintained a familiar metal-oxide-semiconductor (MOS) structure using a polycrystalline silicon gate, a silicon dioxide insulator, and a single crystal silicon channel. However, continued technology scaling brings a number of new design issues, and alternative structures are becoming advantageous. Recently, high-K dielectrics and metal gates have seen widespread adoption to combat rising leakage power consumption. To keep scaling in the future, alternatives to the conventional silicon channel must also be considered. In this chapter, we describe a new class of transistors whose channels are made from semiconducting carbon nanomaterials. These nanomaterials come in two forms: carbon nanotubes (CNTs), and graphene nanoribbons (GNRs). The research community has given specific attention to these two carbon allotropes because of their outstanding electrical properties, including high mobilities at room temperature, high current densities, and micronscale mean free paths. There are many possible transistor designs involving CNTs and GNRs, and each offers a unique set of benefits. They also face a number of challenges. This chapter covers the evolution of these designs, and highlights the works that have driven their development. In order to be useful to the semiconductor industry, transistors must be connected together to form higher order circuits. Therefore, state of the art carbon nanomaterial modeling techniques are reviewed, and their application towards nanoscale VLSI circuit evaluation is discussed. We also introduce logic gates and small scale circuit structures that use these nanomaterial transistors. Throughout the chapter, an emphasis is placed on identifying the opportunities and challenges involved in the adoption of carbon nanomaterial transistors.