Investigation under magnetic field of new quantum structures for infrared and terahertz photonics
Simon Maëro (LPA)


This work reports on the study under magnetic field of three interesting quantum systems, which present remarkable electronic properties and potential applications for infrared and terahertz photonics : two quantum cascade structures, one detector and one emitter, as well as epitaxial graphene layers grown on the carbon face of SiC. The GaAs/AlGaAs quantum cascade detector, designed to work around 15-m, was studied both with and without illumination in order to identify the electronic paths responsible for the dark current and the photocurrent. The development of a photocurrent model allowed us to identify the key points controlling the electronic transport. The investigation, as a function of the temperature and bias voltage, of a InGaAs/GaAsSb quantum cascade laser with a nominally symmetric structure shows the influence of interface roughness on the laser performances. We demonstrate that the InGaAs/GaAsSb type II heterostructure system is promising for developing terahertz quantum cascade lasers working at high temperature. Finally, magneto-spectroscopy experiments performed on epitaxial graphene display, besides the transitions between Landau levels of monolayer graphene, additional signatures that we attribute to disorder, more specifically to carbon vacancies. Calculations using a delta-like potential for modeling the defects are in good agreement with the experimental results. This study is the first experimental demonstration of the influence of localized defects on the graphene electronic properties. The disorder perturbed Landau level structure is clearly established.