Scanning tunneling microscopy has been used to investigate the nucleation and evolution of InAs/GaAs(001) quantum dots (QD’s) grown by molecular beam epitaxy. No scaling behavior as a function of coverage is observed for the QD size distributions during their initial stages of formation. At coverages close to the critical coverage the shape of the QD volume distribution resembles an $i=0\mathrm{}$ scaling curve, and a modified $i=1\mathrm{}$ curve after saturation of the QD number density, with a crossover regime in between. The results show that strain has a significant influence during QD nucleation and the initial stages of growth, but is unimportant in the later stages of QD development. Comparison with classic nucleation theory indicates a large, temperature-dependent size for the critical nucleus $(i=18\mathrm{}$ at 500 °C). This disagrees with conventional models of QD formation and highlights the limited applicability of simple growth theories in modeling complex heteroepitaxial growth systems.

• Received 3 September 2002

DOI:https://doi.org/10.1103/PhysRevB.66.201302