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Free keywords:
Molecular-beam epitaxy; Island formation; Monolayer coverage; Coherent islands, GaAs; Transition; Heteroepitaxy; Stability; InGaAs
Abstract:
InAs quantum dots (QD's) were grown on the GaAs((113) over bar )B surface by molecular-beam epitaxy at temperatures between 435 and 490 degreesC. Their shape, size, and number density were investigated by in-situ scanning tunnelling microscopy. The shape of the QD's is given for the most part by {110}, ((111) over bar )B, and vicinal (00 (1) over bar) bounding facets, and does not change significantly with growth temperature. The diameter at the base and the height of the QD's increase monotonously from 25 to 54 nm, and from 3.5 to 9.8 nm, respectively, whereas the number density decreases as temperature increases. This is explained by assuming a slight decrease of the number density of critical growth nuclei with increasing temperature. The size distribution is bimodal: besides the coherent QD's, some larger and probably incoherent islands are observed that are extended along [33 (2) over bar]. Post annealing increases the diameter and the height by about 30% and decreases the number density, but does not change the shape significantly.
