Controlled Synthesis of InAs Wires, Dot and Twin-Dot Array configurations by
Cleaved Edge OvergrowthE. Uccelli, M. Bichler, S. Nürnberger, G. Abstreiter, A. Fontcuberta i Morral
Nanotechnology 19, 2008
What is it all about?
Control of size and thereby emission properties of QDs is possible but control of position is more challenging
In situ cleaved edge overgrowth to control the nucleation of InAs QDs
Uccelli, Bichler, Nürnberger, Abstreiter and Fontcuberta i Morral
Cleaved Edge Overgrowth- Fabrication I
Left: L. Pfeiffer et al., Appl. Phys. Lett. 56, 1697 (1990)Right: G. Schedelbeck et al., Science 278, 1792 (1997)
Growth of InAs Structures on Cleaved GaAs/AlAs
- Fabrication II
Stranski-Krastanov growth mode
Phenomenological Growth Models
Layer-by-layer
Frank-van der Merve
Layer-plus-island
Stranski-Krastanov
Island
Vollmer-Weber
γs = γsf + γf cosφ
γs ≥ γsf + γf + CkBT ln(p0/p) γs < γsf + γf + CkBT ln(p0/p)
Mechanism for Growth
1 ML = 2.83 Å
MLLLdMLL
Ddh
AlAs
GaAsGaAs
AlAsAlAs
2
Twin-Dot Arrays
BUT! Also growth on GaAs regions
Conclusion
• Atomic precison of MBE used for positioning of QDs and other structures
• Technique seems limited to simple geometries because of the use of cleavage planes
• Small window for preferential growth on AlAs but it is there!
Questions?
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