Influence of bismuth on the formation and properties of InAs/GaAs quantum dots

We have investigated the effects of bismuth on the formation and properties of epitaxial InAs/GaAs multilayers consisting of alternating depositions of sub-monolayers and a few monolayers of size-mismatched species, termed sub-monolayer (SML) epitaxy, in comparison with their Stranski-Krastanov (SK) quantum dot (QD) and quantum well (QW) counterparts. In-situ reflection high-energy electron diffraction reveals reduced indium segregation in the presence of bismuth, suggesting that bismuth serves as a surfactant during InAs epitaxy. For SK-QDs, atomic-force microscopy (AFM) reveals a bismuth-induced enhancement in QD density and size uniformity. Meanwhile, a corresponding bismuth-induced redshift in photoluminescence (PL) emission energy and a bismuth-induced decrease in PL emission linewidth is apparent. We also discuss the influence of bismuth on the 3D topology and local indium and gallium compositions from local-electrode atom-probe tomography (LEAP), and the resulting implications for the optical properties of both SK and SML QD layers. Finally, opportunities for surfactant-mediated tailoring of QDs for optoelectronics will be discussed.