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

MLL

LdMLL

D

dh

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?