Resumo:
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.
