The Energetics of Self-organised InAs/GaAs(100) Quantum Dots
When InAs is heteroepitaxially deposited on GaAs(100), it initially forms as a two-dimensional (2D) layer, but then transforms into a number of three-dimensional (3D) quantum dot structures above a certain thickness. A novel energetic model for this 2D-3D transition is proposed in this paper. This incorporates the effect of strain on the free surface energies of the dot and the effect of the wetting layer (WL) thickness on the excess free energy of the WL. These additional considerations are found to be highly significant. In fact, they are sufficient to effectively reverse the conventional thermodynamic picture of Stranski-Krastanov growth, such that the volumetric term is positive (and not negative) and the surface term is negative (and not positive). This results in the prediction of an equilibrium dot volume which is qualitatively consistent with the observed narrow size distribution in this system. A thermodynamic explanation for the existence of the final WL thickness is also proposed.
KeywordsStrain Energy Density Elastic Strain Energy Surface Strain Wetting Layer Excess Free Energy
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