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HL: Halbleiterphysik

HL 23: Grenz- und Oberfl
ächen II

HL 23.2: Talk

Wednesday, March 29, 2000, 16:15–16:30, H17

Diffusion on strained semiconductor surfaces: In/GaAs(001)-c(4×4) — •Evgeni Penev, Peter Kratzer, and Matthias Scheffler — Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin-Dahlem

In epitaxial growth of III-V compound semiconductors, the quality of the films is often governed by cation diffusivity. However, for heteroepitaxy of strained films, the increasing strain in the pseudomorphic film may affect the diffusivity. We employ first-principles total-energy calculations to study this intriguing possibility. For the example of In/GaAs(001)-c(4×4) we present evidence for a novel strain dependence of the diffusion barriers: Tensile strain is found to lower the diffusion barrier, in contrast to previous findings on metal surfaces. In recent years, island formation in the Stranski-Krastanov growth mode of InAs on the GaAs(001) surface has been exploited for producing self-assembled quantum dots. The strain fields around these coherently strained islands will affect diffusive material transport. Possible implications for self-limiting growth of the InAs islands are discussed.

Since the c(4× 4) reconstruction is built up from a double layer of arsenic terminated by As dimers, incorporation of In requires splitting of the As dimer bonds. We provide new insight into the surface reactivity of In adatoms by mapping the adatom-dimer interaction in a two-dimensional configurational space. During incorporation the In adatom is found to pass through three binding states characterized by different local coordination in the In-As-dimer complex.