Effect of growth rate on the size, composition, and optical properties of InAs/GaAs quantum dots grown by molecular-beam epitaxy

The effect of the InAs deposition rate on the properties of InAs/GaAs quantum dots (QD’s) grown on GaAs(001) substrates by molecular-beam epitaxy has been studied by scanning tunneling 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 μm, 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. We deduce that the composition of the dots is also dependent on the growth rate, the indium fraction being highest at the lowest growth rates. The shifts in the emission wavelength and linewidth correlate with changes in the QD size, size distribution, and composition.