Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 96: Focus Session: Semiconductor Nanophotonics - Characterization on the Atomic Scale

HL 96.5: Invited Talk

Friday, March 30, 2012, 11:45–12:15, ER 164

Atomistic insights and controls for compound semiconductor growth by STMBE: STM obseration during MBE growth — •Shiro Tsukamoto — Anan National College of Technology

High density arrays of quantum dots (QDs) can easily be grown without any need for nano-patterning. These self-assembled QDs are strong candidates for advanced semiconductor laser and quantum devices. However, the precise physical mechanism of self-assembly is not understood, which hampers control over QD size, density and distribution for particular applications. This prototypical self-assembly system also presents very general challenges for growth modeling over scales from atomic dimensions to hundreds of nanometers. Here we show dynamic images of InAs QD formation on GaAs(001) obtained using a unique scanning tunneling microscope (STM) placed within a molecular beam epitaxy (MBE) growth chamber: STMBE. These elucidate the mechanism of QD nucleation, demonstrating directly that not all deposited In is initially incorporated into the lattice, hence providing a large supply of material to rapidly form QDs via islands containing tens of atoms and Kinetic Monte Carlo (KMC) simulations based on first-principles calculations show that alloy fluctuations in the InGaAs wetting layer (WL) are crucial in determining nucleation sites. [1]S.Tsukamoto and N.Koguchi, J.Cryst.Growth 201, 118 (1999). [2]S.Tsukamoto, et. al., Small 2, 386 (2006). [3]T.Konishi and S.Tsukamoto, Nano.Res.Lett. 5, 1901 (2010); Surf.Sci. 605, L1 (2011).[4]T.Toujyou and S.Tsukamoto, Phys.Stat.Sol. (c) 8, 402 (2011); Nano.Res.Lett. 5, 1930 (2010); Surf.Sci. 605, 1320 (2011).