Gh. Kim et al., Tuning the insulator-quantum Hall liquid transitions in a two-dimensional electron gas using self-assembled InAs, PHYS REV B, 61(16), 2000, pp. 10910-10916
We investigate the transport properties of two-dimensional electron gases (
2DEG's) formed in a GaAs/Alo(0.33)Ga(0.67)As quantum well, where InAs has b
een inserted into the center of the GaAs well. Depending on the growth cond
itions, the InAs forms either self-assembled quantum dots or dashes, and du
e to the resulting strain fields repulsive short-range scattering is experi
enced by the conduction electrons in the 2DEG. In a perpendicular magnetic
field there are transitions between quantum Hall liquids at filling factors
nu=1 and nu=2 and the insulating phase. Depending on the amount of InAs co
verage, the degree of disorder in the 2DEG can be varied, changing the rela
tive size of the nu=1 and nu=2 regions in the disorder-magnetic-field phase
diagrams. Thermal studies show a spin gap at filling factor nu=1, which co
llapses as the magnetic field is decreased. Microscopic information about t
he dots was obtained from structural characterization, as well as from cond
uctance measurements through individual dots isolated using a submicron spl
it gate.