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 quant um 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 mum, with the linewidth decreasing from 44 to 27 meV. STM studies on u ncapped dots show that the number density, total QD volume, and size fluctu ation all decrease significantly as the growth rate is reduced. We deduce t hat the composition of the dots is also dependent on the growth rate, the i ndium fraction being highest at the lowest growth rates. The shifts in the emission wavelength and linewidth correlate with changes in the QD size, si ze distribution, and composition.