Thin-film technology for graphene-based electronic devices and circuits
Elsayed, Mohamed; Negra, Renato (Thesis advisor); Lemme, Max Christian (Thesis advisor)
Aachen (2019) [Dissertation / PhD Thesis]
Page(s): 1 Online-Ressource (xii, Aii, 154 Seiten) : Illustrationen, Diagramme
This dissertation summarizes my research in graphene-based technology, devices and circuits within the Graphene Flagship project funded by the European Commission. The kick-off of the project was in October 2013 after only nine years from the rise of graphene in 2004 as a promising 2D material. In 2013, the status of graphene-based devices was beyond the expectations from the electrical features of graphene. The zero-bandgap nature of the intrinsic graphene leads to challenges in fabricating graphene field-effect transistors (GFET)s which can be employed in conventional circuits like other semiconductor devices. One of these challenges is the poor maximum frequency of oscillations (fmax) which is poor compared to the expected from the charge carrier mobilities. In addition, the poor on-off currents ratio imposes challenges to employ GFETs in Boolean logic gates and thus in digital circuits. This work addresses these challenges by expressing the roadmap of the evolution of GFETs and the employment of these transistors in circuits and systems. Thenceforth, a novel graphene-based device which is the chemical vapor deposition (CVD) metal-insulator-graphene (MIG) diode is presented. The MIG diode is the core contribution of this work by leveraging an interesting feature of graphene which is the graphene quantum capacitance (GCQ). The novel device which uses a similar structure of the thin-film metal-insulator-metal (MIM) diodes but with a distinct charge transfer mechanism allows the implementation of thin-film technology that is employed in high frequency circuit applications. Physical operation of the diode is studied and compared to state-of-the-art MIM diodes showing superior performance in-terms of asymmetry and nonlinearity. Large- and small-signal models are extracted from the characterisation of the fabricated diodes to enable the use of these diodes in circuit applications. In addition, physical design considerations are carried out to ensure high frequency operation of these diodes. An in-house, thin-film monolithic microwave integrated circuit (MMIC) technology integrating MIG diodes together with high quality passives is presented and tested. Different integrated circuits employing the MIG diodes such as power detectors and mixers are implemented at micro and millimetre-wave frequencies. In addition, thin-film Boolean logic gates are presented thanks to the excellent switching properties of MIG diodes. Another attainment of this work is leveraging MIG diodes in six-port topologies which offer a solution to build receivers at different frequency bands of operation. In that regard, a lumped-element six-port junction is implemented on a glass substrate. Owing to the stable MMIC process together with the repeatability of the CVD MIG diodes successful receiver operation is demonstrated. Last but not least, the employment of the unique properties of the GCQ in parametric amplifier (PAMP) topology to realise canonical transmitter and receiver frontends with positive conversion gain is explored and discussed for the first time.