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

MBE Growth of Self-Assembled InAs and InGaAs Quantum Dots Embedded in
Silicon Matrix
Figure 5.30: (1 × 1 µm 2 ) AFM images of 4 ML In 0.5 Ga 0.5 As QDs at growth temperature
of 500 ◦ C on buer Si, grown on Si (100) substrate with dierent V/III ratio. (a)
10. (b) 20. (c) 30.
and density. Therefore, from the previous study one can summarize the optimized
growth conditions based on morphology study with homogeneous size distribution
of diameter (D) in the range of 15 - 25 nm, height (H) ranging from 3 - 7 nm and
dots density of ∼ 10 11 cm −2 . An optimized homogeneous dot size and density was
found to be with 4 MLs coverage of In 0.5 Ga 0.5 As QDs and V/III ratio of 20 grown
at 500 ◦ C. Under these optimized growth conditions based on AFM morphology
analysis as discussed before, 4 MLs In 0.5 Ga 0.5 As QDs were grown at 500 ◦ C and
V/III ratio of 20 in silicon matrix for photoluminescence measurements. However,
the capped structure did not show so far any optical emission, most probably due
to the formation of mist dislocations at the interface of In 0.5 Ga 0.5 As/Si and MTs
and SFs defects inside the dots which act as irradiative centers for any optical
activity.
As a conclusion, in comparison with InAs QDs a dierent growth scenario
of In 0.5 Ga 0.5 As has been observed. Firstly, In 0.5 Ga 0.5 As QDs formation were
observed at higher temperature of 500 ◦ C (Fig. 5.28) compared to no InAs QDs
formation at the same temperature (Fig. 5.6). However, this most probably due to
higher Ga desorption temperature compared to Indium. Moreover, In 0.5 Ga 0.5 As
did not show density dependence with V/III ratio in the range of 10 - 30 (Fig. 5.31)
compared with strong density dependence observed in InAs system (Fig. 5.7), due
to dierent nucleation mechanism.
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