Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

MBE Growth of Self-Assembled InAs and InGaAs Quantum Dots Embedded in
Silicon Matrix
Figure 5.8:
(1 × 1 µm 2 ) AFM images of 2 MLs of InAs QDs grown using SK mode
with dierent indium (In) growth rates (a) 108 nm/h (circular InAs QDs) and (b) 324
nm/h (dash-like QDs).
The observed shape transition is due to the preferential migration of indium
atoms along [110] crystal direction, resulted from the anisotropic migration
lengths of indium atoms [85].
Fig. 5.9 shows the dependence of dierent growth parameters on their main
structural properties such as density, lateral size, height of InAs QDs.
From
this study, one can conclude that the optimized growth parameters of InAs QDs
can be identied morphology wise. The growth temperature should be set below
450 ◦ C, which is an essential condition for InAs QDs formation and can avoid any
additional indium desorption, which is signicantly starts above this temperature
[3]. A low growth rate of 108 nm/h resulted in circular QDs shape formation.
However, average dots densities with non-overlapping dots can be achieved with
a V/III ratio of 25 as well as with an InAs coverage less than 5 MLs.
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