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Self-assembled InAs quantum islands (QIs) fabricated on InP(001) by solid source molecular beam epitaxy (SSMBE) in the Stranski-Krastanow regime are investigated by means of photoluminescence (PL), and polarization of photoluminescence (PPL) techniques. Photoluminescence measurements as a function of excitation power show that multi-component PL spectra are related to emission coming out from transitions associated to ground and excited states of InAs quantum islands. A value of 22 meV at 8K for the FWHM of the ground state PL peak is measured and reveals a narrow island size distribution. A degree of linear polarization of about 30% indicates that the InAs quantum islands are elongated in the [1-10] direction. The temperature dependence of the integrated PL intensity has been also studied. The integrated PL intensity remains very strong at room temperature, as much as 49% of that at 8 K, indicating a strong spatial localization of the excitons in the InAs QIs. The temperature dependent data show an Arrhenius behavior characterized by two activation energies. An analysis of this dependence indicates that the main loss mechanism is due to dissociation of excitons in the InP barrier.