Understanding the growth mode transition in InAs/GaAs(0 0 1) quantum dot formation

Scanning tunneling microscopy has been used to monitor the growth by molecular beam epitaxy of InAs quantum dots (QDs) on GaAs(0 0 1) at and near the critical coverage (θcrit). Direct evidence is obtained for the existence of small irregular 3D islands of height 6–12 Å (2–4 ML) which contain ∼150 atoms or more. These features develop rapidly (within 0.05 ML of θcrit) into regular mature QDs with an average volume >1 × 104 atoms. Scaling analysis of the QD size distributions suggests that strain may have a significant influence during QD nucleation and the initial stages of growth, but is unimportant during the later stages of QD development.