The growth-temperature dependence of the optical spin-injection dynamics in self-assembled quantum dots (QDs) of In0.5Ga0.5As was studied by increasing the sheet density of the dots from 2 x 10(10) to 7 x 10(10) cm(-2) and reducing their size through a decrease in growth temperature from 500 to 470 degrees C. The circularly polarized transient photoluminescence (PL) of the resulting QD ensembles was analyzed after optical excitation of spin-polarized carriers in GaAs barriers by using rate equations that take into account spin-injection dynamics such as spin-injection time, spin relaxation during injection, spin-dependent state-filling, and subsequent spin relaxation. The excitation-power dependence of the transient circular polarization of PL in the QDs, which is sensitive to the state-filling effect, was also examined. It was found that a systematic increase occurs in the degree of circular polarization of PL with decreasing growth temperature, which reflects the transient polarization of exciton spin after spin injection. This is attributed to strong suppression of the filling effect for the majority-spin states as the dot-density of the QDs increases. (C) 2014 AIP Publishing LLC.