Photoreflectance (PR) measurements are performed as a function of temperature on self-organized InAs/InP(0 0 1) quantum sticks (QSs) grown by solid-source molecular beam epitaxy. With a very weak excitation power, three PR transition energies are arising and associated with the ground state and two excited states, respectively, in good agreement with both photoluminescence (PL) and PL excitation measurements. The temperature dependence of the PR transition energies is in good agreement with the Bose–Einstein behavior. From PL analysis of these InAs/InP QSs, the ground state was assumed to be partially filled because of the residual n-type doping of the InP barrier layers. The PR spectra analysis allows us to further confirm this assumption, considering mainly the relative PR intensity of the different transitions, as well as the Franz Keldysh oscillations (FKO) above the InP bandgap.