Published in Appl. Phys. Lett. 97, 123110 (2010).
Electronic States of InAs/GaAs Quantum Dots by Scanning Tunneling Spectroscopy
S. Gaan (a), Guowei He (a), R. M. Feenstra (a),
J. Walker (b), and E. Towe (b)
(a) Dept. Physics, Carnegie Mellon University, Pittsburgh, PA 15213
(b) Dept. Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213
InAs/GaAs quantum-dot heterostructures grown by molecular-beam epitaxy are studied using cross-sectional scanning tunneling microscopy and spectroscopy. Individual InAs quantum dots (QDs) are resolved in the images. Tunneling spectra acquired 3-4 nm from the QDs show a peak located in the upper part of the GaAs bandgap originating from the lowest electron confined state, together with a tail extending out from the valence band from hole confined states. A line-shape analysis is used to deduce the binding energies of the electron and hole QD states.
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