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

MBE Growth of InAs and InGaAs Quantum Dots Embedded in GaAs Matrix
Figure 6.4: (a) The RHEED patterns of Silicon surface after the thermal oxide desorption
at 850 ◦ C and (b) at 750 ◦ C. The AFM image (5×5 µm 2 ) of the patterned Si
surface after the thermal cleaning at 850 ◦ C and (d) a (3×3 µm 2 ) at 750 ◦ C.
The removal of oxide desorption was conrmed by semicircular streaky RHEED
patterns (Fig. 6.4(a)) indicating a 2D smooth surface. However, the annealing
at 850 ◦ C have severely damaged the pattern as it is observed in AFM image
of the surface (Fig. 6.4(c)). By reducing the annealing temperature to 750 ◦ C
and annealing for 30 min till the emergence of a 2D semicircular RHEED pattern
(Fig. 6.4(b)), the pattern can be preserved as shown by the AFM prole
(Fig. 6.4(d)).
No detectable dierence in the diameter, depth and vertical prole of the holes
was observed before and after the optimized in-situ cleaning. This observation
was conrmed from the high resolution single hole AFM measurement shown in
Fig. 6.5. The lateral size (L) of the hole before in-situ treatment was in the
range of 70-75 and the depth (D) around 70 nm Fig. 6.5(a). Slightly smaller
values were observed after in-situ surface treatment (Fig. 6.5(b)). The HR-AFM
single hole measurements proved that the holes dimensions were preserved after
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