Guest seminar: GaAsSb Quantum Structures: From Nested to Staggered Bandoffsets

Thursday 16 Jun 2022, 16:00 → 18:00 Europe/Stockholm

K 404 (Department of Physics)

Professor Rachel S. Goldman from the University of Michigan, Ann Arbor, will give a presentation on GaAsSb Quantum Structures.

Abstract
Due to the predicted strain and composition dependence of nested (type I) vs staggered (type II) band alignments, GaAsSb quantum structures are useful for devices that rely upon electron-hole recombination and spatial separation of charge carriers. Within GaSb/GaAs multilayers, atomic structures ranging from dots to rings to clusters, with or without dislocations, have been observed. However, the association of
nanostructure morphologies with emission energies and band offset types have remained elusive. We use a combined computational-experimental approach to investigate the morphology, confinement energies, and band offsets of GaSb/GaAs multilayers. The computed confinement energies and the measured photoluminescence emission energies increase from QDs to QD-rings to 2D layers, enabling direct association of nanostructure morphologies with the optical properties of the GaSb/GaAs multilayers [1]. For GaSb/GaAs QDs, misfit strain induces a transition from type I to type II band alignment. Although dislocation-induced strain relaxation prevents the type I to type II transition, electrostatic charging at dislocations induces the staggered band alignment once again [2]. Further work is in progress to explore correlations between local QD morphologies, dislocation configurations, and local band alignments in QD ensembles.

1. C.M. Greenhill, A.S. Chang, E. Zech, S. Clark, G. Balakrishnan, R.S. Goldman, "Influence of QD Morphology on the Optical Properties of GaSb/GaAs Multilayers", Appl. Phys. Lett. 116, 252107 (2020).

2. B.C. McGuigan, A.S. Chang, C.M. Greenhill, H.T. Johnson, R.S. Goldman, "Influence of Strain and Dislocations on GaSb/GaAs Quantum Dots: From Nested to Staggered Band Alignment", J. Appl. Phys. 131, 085703 (2022).

This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Grant No. DE-FG02-06EF46339. The work was also supported, in part, by the National
Science Foundation through the Graduate Research Fellowship Program (No. DGE-1256260) and Grant No. ECCS-1610362.

Biography:
Rachel S. Goldman is Professor of Materials Science & Engineering, Physics, and Electrical Engineering & Computer Science at the University of Michigan. She is Associate Director of Applied Physics, and has served as MSE Graduate Chair, Associate Director of the DoE Energy Frontiers Research Center, and Education Director of the NSF Materials Research Science and Engineering Center. Prof. Goldman's research emphasizes the role of local solute configurations on novel functionalities of semiconductor alloys and nanostructures. She has published > 135 papers on processing-structure-property correlations in semiconductors; she holds a U.S. patent on “ion-cut-synthesis”, a novel approach for simultaneous synthesis and integration of nanocomposite materials with virtually any substrate. Recently, she pioneered the incorporation of Writing to Learn pedagogies into introductory materials science and engineering courses. Prof. Goldman is a Fellow of the American Physical Society (APS), the American Association for the Advancement of Science, and the American Vacuum Society. She is Associate Editor of the Journal of Applied Physics and Past Chair of the APS Division of Materials Physics