two-to-three dimensional transition in the InAs/GaAs(001) heteroepitaxial growth
Abstract
Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy have been used to study subsequent stages of the heteroepitaxy of InAs on GaAs(001), from the initial formation of the pseudomorphic strained two-dimensional wetting layer up to the self-assembling of three-dimensional quantum dots (QDs). We provide evidence of structural features that play a crucial role in the two-to-three-dimensional transition and discuss their contribution to the final morphology of the self-assembled nanoparticles. The features to be considered, close to the 2D-3D transition, are: large and small 2D-islands one-monolayer high, small quasi-3D islands of height £2 nm, 3D QD of height 3-4 nm. Although reported several times, definite conclusion on the role of these features in QD nucleation is not yet achieved. 2D-features contribute only as step edge by supplying nucleation sites. Statistical data show clearly separated distributions for the quasi-3D QD and the 3D-QD and the gap between them does not fill in at any InAs deposition. These observations are consistent with the existence of two equilibrium sizes for the 3D islands, one of which (quasi-3D QD) is stable only for a limited range of InAs thickness. No clear evidence exists that the nucleation of quasi-3D QD is the first step of the self-assembling QD. A model is suggested for the strained phase at the critical thickness consisting of an intermixed In_xGa_1-xAs and InAs ``floating'' on top. Such ``floating'' phase participate to the large mass-transport along the surface during the two-to-three-dimensional transition that accounts for the total volume of dots.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MAR.K1070P