  The electronic structure of InAs quantum dots covered with the GaAs(1-y)Sb(y)
strain reducing layer has been studied using the k.p theory. We explain
previous experimental observations of the red shift of the photoluminescence
emission with increasing y and its blue shift with increasing excitation power.
For y>0.19 type-II dots are formed with holes localized in the GaAsSb close to
the dot base; two segments at opposite sides of the dot, forming molecular-like
states, result from the piezoelectric field. We also propose an experiment that
could be used to identify the hole localization using a vertical electric
field.
