The effect of the InAs deposition rate on the properties of InAs/GaAs quantum dots (QDs) grown on GaAs (0 0 1) substrates by molecular beam epitaxy has been studied by scanning tunnelling microscopy (STM) and photoluminescence (PL). PL studies performed on GaAs capped QD samples show that the emission wavelength increases with decreasing growth rate, reaching a maximum around 1.3 mum, with the linewidth decreasing from 44 to 27 meV. STM studies on uncapped dots show that the number density, total QD volume and size fluctuation all decrease significantly as the growth rate is reduced. The observed shifts in the emission wavelength and linewidth are attributed to changes in the QD size, size distribution and composition.