Growth mechanisms for InAs/GaAs QDs with and without Bi surfactants

We report systematic study of growth of self-assembled InAs quantum dots (QDs) on GaAs substrate at various temperatures with and without exposure of bismuth surfactants. Results show that the coalescence amongst InAs QDs is considerably inhibited by the exposure of bismuth flux during growth in the temperature range from 475 to 500 degrees C, leading to improved dot uniformity and a modified dot density. The mechanism of the suppression effect by bismuth surfactants on the strain-induced islanding through inhibiting the indium adatom mobility and the evaporation rate on the surface kinetically is thus clarified for the growth of InAs QDs. The photoluminescence peak wavelength for the InAs QDs with Bi exposure red shifted slightly due to the suppression of Bi atoms on the QD dissolution during the capping process at higher temperatures. Moreover, by investigating the temperature-dependent quenching processes with and without Bi exposure, it is observed that the the weak carrier confinement occurred in QDs with the presence of Bi caused broadness in the linewidths.