Carrier trapping and optical properties of InAs/InP quantum dashes

We model the optical properties of semiconductor InAs/InP quantum dashes (QDashes), that is, highly elongated quantum dot structures. These structures are often characterized by a non-uniform shape and the presence of width fluctuations. We show that such shape irregularities can act as additional trapping centers within the confinement volume of a QDash and strongly influence its optical properties. We show how the optical transition rates depend on various QDash shape parameters (e.g., amplitude and position of the widening of the structure) and study the polarization properties of radiation emitted by the system. We confirm that the presence of a QDash width fluctuation leads to a strong localization of the exciton ground state, which results in a reduction of its anisotropy, in spite of the strong elongation of the whole structure. Such a character of the confining potential not only manifests itself by a reduced value of the degree of linear polarization of the exciton ground state, but also strongly affects the properties of higher energy excitonic states.