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strain field, the InAlAs islands act as nucleation
centers for the following InAs dots; as in the present
work a uniform dense array (d ~1.5 × 1011 cm–2) of
small size dots is observed, which confirms the pri-
mary importance of the Al for the growth mechanism
of dots nucleated on layers containing this element.
CONCLUSION
InAs islands have been grown by molecular beam
epitaxy on InAlAs pseudomorphic and metamorphic
buffer layers and exhibit higher densities and smaller
size as compared with InAs islands grown on GaAs.
The presence of more nucleation sites (steps on the
rougher InAlAs surface) accounts for these high den-
sities. Less surface mass transport is observed on the
InAlAs buffer layers and strain relaxation in the
metamorphic buffer delays the coalescence of the
InAs islands. The increase of the indium molar frac-
tion in the InAlAs templates results in a transition
from islands to wires, due to the anisotropy of surface
diffusion of the adatoms and the lowering of the
mismatch strain with InAs.