Non-Equilibrium Optical Properties Of Encapsulated Graphene

A multitude of existing technologies are based on the ability of converting light into electrical signals. Graphene has demonstrated a number of optical and transport properties [1] which are promising for this type of optoelectronic applications and great efforts have been devoted to the development of graphene-based photodetectors. Being a gapless semiconductor, graphene enables light absorption over a wide energy spectrum, spanning from the ultraviolet to the far infrared. Moreover, its absorption is wavelength-independent and its optical properties are tunable via electrostatic doping. Finally, it displays low dissipation rates and high carrier mobility and it enables electromagnetic-energy confinement to extremely small volumes [2]. However, graphene devices on standard SiO2-substrates display properties that are far inferior to that of the suspended graphene. This motivates the research for dielectrics that allow substrate-supported geometry while retaining the intrinsic quality of graphene. The photodetection efficiency is ultimately defined by the magnitude and the speed of the photoresponse of the detecting-material.