Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 17: Focussed Session: Atomic Scale Characterization

HL 17.2: Invited Talk

Tuesday, March 13, 2018, 10:00–10:30, EW 202

Total Tomography of Nonplanar Heterostructures: Doping and Confinement Pontentials — •Lincoln Lauhon — Northwestern University, USA

The direct visualization of nanoscale structure enables the development of predictive models of novel physical behaviors. The talk will discuss recent advances in the nanoscale tomography of non-planar III-As semiconductor heterostructures including narrow gap III-As nanowire and related heterostructures for next generation compact light sources and novel computing schemes. Atom probe tomography is used to visualize the distribution of atoms in three dimensions with nanoscale resolution, providing new insights into growth mechanisms and the resulting the distribution of dopant atoms. Of particular interest is the evolution of composition of AlGaAs barrier layers and InGaAs quantum wells and nanowires when multiple growth facets are present. Generically, we find that alloy composition and doping rates vary considerably with surface faceting and polarity. Three-dimensional maps of the composition, when combined with appropriate models, reveals how the confinement of electrons and photons is influenced by size, shape, and interfaces, providing a foundation for device engineering. The tomography effort has recently been expanded to include 3-D mapping of strain using x-ray Bragg projection ptychography. The novel combination of atom probe tomography and x-ray ptychography illuminates a route to the total tomography of nanostructures.