Rachel S. Goldman

Professor

rsgold@umich.edu

2094 H.H. Dow Building

T: (734) 647-6821

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Structure-Property Correlations: Confined States in Nanostructures

Collaborators: H. T. Johnson, UIUC
Sponsor: Army Research Office DAAD 19-01-1-0462
Understanding electronic states in dimensionally-confined semiconductor structures is critical for technologies ranging from IR detection to quantum computation. Further advances in many applications will require a narrowing of the density of states, which may be achieved through an improved understanding and control of the electronic effects of QD composition, size, and shape. For example, a number of critical fundamental questions regarding the effects of size, interface disorder, and point defects on the electronic states of semiconductor nanostructures remain unanswered: How many atoms are needed in a QD for it to cross over from behaving as an impurity state to a band of states? How does a diffuse interface affect the QD band structure and positions of confined states? How do point defects and strain affect the electronic states of QDs? Specifically, we are interested in understanding the effects of nanostructure size, shape, strain, and interface disorder on the electronic band structure and confined states.
Highlights (Click an image for more information)
  • Spectroscopy Across a Single Quantum Dot

    We are exploring the effect of composition gradients on the electronic states in individual (uncoupled) QDs. STS spectra taken across single QDs reveal a small effective bandgap at the core, and a more substantial effective bandgap near the edge, suggesting the presence of bulk-like InAs near the center and significant quantization near the QD edge. The effective bandgap across the smaller QD is larger than effective bandgap across the larger QD, suggesting a difference in quantization across QDs of different sizes, with carrier confinement being higher in smaller sized QDs.