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Graphene devices


At IHP graphene device research is focused mainly on high frequency transistors for analog applications. Recently, it was demonstrated that graphene-based field-effect transistors (FETs) can operate at very high frequencies exceeding those achievable in standard Si MOSFET technology for devices with similar gate lengths [5]. It is expected that graphene-based transistors can in future enable operation frequencies in the THz domain and thus outperform currently existing semiconductor technologies. However, up to date fabricated graphene FETs (GFETs) suffer from some fundamental problems like e.g. lacking drain current saturation which may prevent GFETs from applications in high frequency circuits. For this reason further work on optimization of RF GFETs is required.

Fig. 7: Secondary electron microscopy image of a radio frequency graphene transistor fabricated in collaboration with Max Planck Institute in Halle.

To fully exploit the unique properties of graphene beside standard RF GFETs novel graphene device concepts are explored at IHP. One of the examples is the graphene base transistor (GBT, Fig. 8). In a GBT, the graphene layer is sandwiched between two insulator layers and two metal layers. The first metal layer functions as an electron emitter and the second metal layer as a collector. The graphene layer acts as a base electrode which controls the flow of electrons from the emitter to the collector [6]. Since the graphene base electrode is ultrathin and exhibits a very low resistivity the proposed device is expected to be capable of operation at very high frequencies extending into the THz regime.

Fig. 8: Schematic cross-section of a graphene base transistor (GBT, left) and a graphene field-effect transistor (GFET, right).

First proof-of-concept GBT devices demonstrating DC functionality have been fabricated in collaboration with KTH and the results published in Nano Letters (http://pubs.acs.org/doi/abs/10.1021/nl304305x) [7].

The building and the infrastructure of the IHP were funded by the European Regional Development Fund of the European Union, funds of the Federal Government and also funds of the Federal State of Brandenburg.