We studied InAs self-assembled island formation as a function of the growth rate and examined the effects of overgrown layers on the light emission features. The InAs islands were grown by a conventional molecular beam epitaxy on GaAs. We found that the island size and density strongly depended on the growth rate. With a reduction in the growth rate, the island size increased and the light emission wavelength correspondingly shifted to the longer side. The emission wavelength reached 1.3 mu m when the growth-rate was reduced to 2 x 10(-3) monolayer (ML)/s, but the island density decreased (5 x 10(9) cm(-2)). We also confirmed that the emission wavelength red-shifted when islands were covered by InGaAs alloys, depending on both the thickness and In composition. Using a combined method, growing islands at a growth rate in the middle range and embedding islands with InGaAs layers, we obtained relatively high density islands with a light emission at 1.3 mu m. We confirmed room-temperature lasing from these quantum dots with a threshold current of 8 mA under continuous wave conditions.