Eurocores_EuroGRAPHENE_1.Call_Electrical and Optoelectrical Graphene Devices( ELOGRAPH)

This project is part of a joint project aiming at the development of graphene-based field-effect-transistors (FETs) and photodetectors, their quantitative characterization, and physical modeling. Numerical simulation will be used to improve the physical understanding of the functioning of these electronic and opto-electronic devices. It also provides a means for device design and performance optimization. To introduce a band gap in graphene, two classes of nano-structures are considered, namely graphene nano-ribbons and anti-dot superlattices. The electronic band structure of these nano-structures is studied using the tight-binding method, and design parameters are derived from the theoretical calculations. Based on the electronic structure, the optical transition rates between different sub-bands are determined. The tight-binding method is known to be computationally efficient and can be well used in conjunction with transport calculations. A suitable model for the devices considered has to address various effects: Quantum mechanical confinement, tunneling and interference, coupling of the semiconductor region to the contacts (open systems), non-equilibrium conditions (voltage applied to the contacts, irradiation), electron-phonon scattering, electron-photon interaction, and space charge effects. The non-equilibrium Green`s function (NEGF) formalism has proven well suited for the numerical study of such problems. In a first stage, a quantum-ballistic transport model will be implemented and applied to the considered nano-structures. In a second stage, both elastic and inelastic scattering mechanisms due to acoustic and optical phonons are included. Scattering broadens the density of states, which in turn will affect significantly the optical properties of the device. The effect of these scattering mechanisms on the optical transition rates is investigated. The device simulator for graphene- based FETs and FET infra-red photo detectors will extensively be used to analyze this new class of opto-electronic devices. The choice of the metal for the electrodes and of the geometrical parameters has a strong effect on device performance. Ways to optimize the electrical and opto-electrical characteristics of the devices by appropriate tuning of these design parameters are theoretically investigated.

Graphite-related materials such as fullerenes, carbon nanotubes, and graphene have been extensively studied in recent years due to their exceptional electronic, optoelectronic, and thermal properties. Graphene, a one-atomic carbon sheet with a honeycomb lattice, has attracted significant attention due to its unique physical properties. This material shows extraordinarily high carrier mobility and is considered to be a potentially high speed transistor material. In this work the role of geometrical parameters and non-idealities on graphene-based devices for electronic, optical, and thermoelectric applications are numerically studied. The results provide a deeper insight into operation of graphene devices. In addition, compact models are developed which pave the way for future circuit and system level analysis and optimization studies.