Fenômenos de transporte em superredes de InAs/GaAs contendo pontos quânticos

Abstract

Self-assembled quantum dots are in the center of interest of both fundamental and applied research. In this work, van der Pauw resistivity, Hall effect and I(V) measurements are applied to obtain the mobility on a series of Molecular Beam Epitaxy InAs/GaAs superlattices samples containing InAs quantum dots, grown in the Stranski-Krastanov mode. Three growth parameter were varied: the InAs coverage, the number of repetitions of the InAs/GaAs layers and the GaAs spacer thickness. The measurements were done in a 5K to 310K temperature range. The results presenting samples with low resistivity and the mobility dependence on the temperature were adjusted in order to evaluate the applicability of the known scattering models. Due to quantum confinement at the GaAs/InAs interface, all scattering mechanisms were considered for a two-dimensional electron gas. The evaluated scattering mechanisms were deformation potential scattering, piezoelectric scattering for acoustic phonons, polar optical scattering for optical phonons and ionized impurity scattering. The scattering by ionized impurities revealed dominant at the low temperatures and the polar optical scattering at high temperatures. The model of scattering by ionized impurities gives information about the impurities concentrations. The analysis of the carrier concentration evidenced that properties like form, size, density and symmetry of quantum dots influence more the electrical properties at the low temperatures, below 30K. The I(V) characterization presents nonlinear electrical behaviors at the high electrical fields intensities and under infrared radiation.