Abstract
The growth mode of InAs/GaAs(111)A is systematically investigated using our macroscopic theory with the aid of empirical potential calculations that determine parameter values used in the macroscopic theory. Here, stacking-fault tetrahedron (SFT) found in InAs/GaAs(111)A and misfit dislocation (MD) formations are employed as strain relaxation mechanisms. The calculated results reveal that the MD formation occurs at the layer thickness h about 7 monolayers (MLs). Moreover, we found that the SFT forming at h about 4 MLs makes surface atoms move upward to reduce the strain energy to promote the two dimensional (2D) growth. Therefore, the SFT in addition to the MD plays an important role in strain relaxation in InAs thin layers on GaAs(111)A. The macroscopic free energy calculations for the growth mode imply that the InAs growth on the GaAs(111)A proceeds along the lower energy path from the 2D-coherent (h ≤ 4 MLs) to the 2D-MD (h ≥ 7 MLs) via the 2D-SFT (4 MLs ≤ h ≤ 7 MLs). Consequently, the 2D growth on the InAs/GaAs(111)A results from strain relaxation due to the formation of the SFT near the surface and the subsequent MD formation at the interface.
Highlights
Low-dimensional nanostructures have received much attention from the scientific and engineering viewpoints because of their small size and large surface-to-volume ratios
Strain relaxation in the InAs/GaAs(111)A heteroepitaxy has been observed by scanning tunnelling microscopy (STM), where the misfit dislocation (MD) network formation is identified as a strain relaxation mechanism occurring at layer thickness h = 3 monolayers (MLs) [3]
On the basis of the model observed by STM, energy calculations using the valence force field (VFF) model clarify that the semicoherent interface consisting of a network of intersecting MDs at h ≥ 4 MLs fully relieves the strain at the interface [13]
Summary
Low-dimensional nanostructures have received much attention from the scientific and engineering viewpoints because of their small size and large surface-to-volume ratios. Rocking-curve analysis of reflection high-energy electron diffraction (RHEED) reveals that elastic distortion of InAs lattice during layer-by-layer growth is found only below 1.5 MLs. the RHEED analysis indicates that strain in the direction parallel to the surface drastically relaxed in the range of 1.5 MLs ≤ h ≤ 3 MLs, while its lattice constant gradually approaches that of bulk InAs at h ≥ 3 MLs [14]. The RHEED analysis indicates that strain in the direction parallel to the surface drastically relaxed in the range of 1.5 MLs ≤ h ≤ 3 MLs, while its lattice constant gradually approaches that of bulk InAs at h ≥ 3 MLs [14] These results are consistent in some aspects, the strain relaxation process depending on layer thickness is still unclear. The SFT with nano- to micro-meter size is often found in InAs layers on GaAs(111), where the SFT is surrounded by the (111)A surface and three triangular {111}-stacking-fault planes consisting of wurtzite structure below the surface [15]
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