Exploring the formation of InAs(Bi)/GaAs QDs at two growth-temperature regimes under different Bi supply conditions.
The effect of a Bi supply on the development of InAs/GaAs (001) QDs has been structurally explored in two growth temperature regimes, one for Bi alloying (380 degrees C) and another for conventional formation of InAs QDs (510 degrees C). At high growth temperature (HT), there is no trace of Bi incorporation into the film and Bi acts as a surfactant limiting the diffusion length of In. All HT QDs are coherent and free of defects with an inverted coneshaped In distribution. Increasing the Bi supply increases both the QD size and the In content (up to 40 %), while decreasing their areal density. At low temperature (LT), the addition of Bi goes beyond the surfactant role, promoting the transformation of the growth mode from 2D to 3D, resulting in an exponential increase in the QD size with Bi supply. Based on size, these LT QDs are divided into two populations in which the larger QDs relax plastically through the formation of misfit dislocations. LT QDs grown under a Bi flux reach a higher In content (80 %) with a homogeneous distribution within them. Remarkably, incorporation of Bi into larger QDs has been detected but it is not homogeneously distributed.