Abstract:

The field-effect transistor (FET) is the building block of both analogue and digital electronics, therefore, it is the basic electronic device that is deeply studied during telecommunication and electronic engineering degrees. In particular, FETs are devices with three terminals, namely, source, gate, and drain where the control of the flow of electrical current between source and drain is realized by the application of a voltage to the gate terminal, which in turn alters the conductivity between the drain and source. FETs are based on conventional semiconductors, like Silicon, Germanium or III-V compounds commonly characterized by unipolar conduction because they involve single-carrier-type operation. In other words, FETs use either electrons (negative charges) or electronic holes (positive charges) as charge carriers in their operation, but not both. This scenario has, however, changed drastically, after the 2010 Nobel prize in physics awarded to Prof. Geim and Prof. Novoselov “for groundbreaking experiments regarding the 2D material graphene”. The research on graphene, which is an ambipolar material, and related materials (GRMs) electronics has grown drastically with the European Commission launching the Graphene Flagship (GF), the biggest research initiative consisting of a 1-billion-euro investment in research and development for 10 years. GRM-based devices could offer big opportunities in many fields such as high-frequency electronics and they have become potential candidates for the deployment of emergent flexible and wearable electronics. This scenario is of particular relevance for the students in telecommunications and electronics degrees, who will face the new challenges arising with this potential paradigm shift in the prevailing electronic technology.

In this context we have implemented a set of circuit models to be exploited in conventional circuit simulators used in engineering degrees. The models capture the physics of the graphene-based FETs, characterized by the ambipolar conduction, and its resulting V-shaped transfer characteristics (current vs. gate voltage). These models can be exploited by the engineering students to explore ambipolar electronics opening the possibility to: 1) redesigning and simplifying of conventional circuits; and 2) seeking of new functionalities in both analogue/RF and digital domains. In this regard, as an example by just considering that the V-shaped transfer characteristics behaves as a parabola, we present new insights for the design of graphene-based microwave amplifiers, mixers, shifters and frequency multipliers that specifically exploit the inherent intrinsic ambipolarity of graphene from an engineering perspective.

Keywords:

Ambipolar, electronics, engineering, graphene, microwave, radiofrequency, teaching.