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HL: Fachverband Halbleiterphysik

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

HL 96.4: Topical Talk

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

Atomic imaging of binary and quaternary semiconductor nanostructures by cross-sectional STM — •Andrea Lenz — Technische Universität Berlin, Berlin, Germany

In cross-sectional STM (XSTM) experiments typically layered semiconductor samples are cleaved in an ultrahigh vacuum system, laying bare an atomically clean cleavage surface. Therewith buried nanostructures can be analyzed with atomic resolution, providing access to their spatial structure and stoichiometry as it also appears in devices.

This contribution will focus first on the atomic structure of binary InAs submonolayer depositions on GaAs(001), demonstrating that the InAs is not located within a single atomic plane, but segregated along growth direction. In addition, the segregation along growth direction is determined in detail by the analysis of the local lattice parameter. Both demonstrate that the strain-induced segregation processes occurring during overgrowth defines the resulting nanostructures. Second, the atomic composition of quaternary InGaAsP layers grown latticed matched on InP(001) is analyzed at both the (110) and the (-110) cleavage surfaces, together yielding two different phase separation effects on different length scales: a formation of columnar structures with widths of some tens of nm and a CuPt-like ordering on the atomic scale. The latter can be identified at the (-110) cleavage surface by alternating brighter and darker atomic rows aligned along the [110] direction, with a periodicity along the [001] growth direction of two lattice constants, as well as by atomic chains of similar brightness oriented along the [-112] and [1-12] directions at the (110) cleavage surface.