Morphology of GaAs-quantum-well interfaces grown by liquid-phase epitaxy

U. Morlock, J. Christen, D. Bimberg, E. Bauser, H.-J. Queisser, and A. Ourmazd
Phys. Rev. B 44, 8792 – Published 15 October 1991
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Abstract

A quasicolumnar structure of GaAs quantum wells with mean column diameters of d=1–10 μm is observed in narrow Al0.4Ga0.6As/GaAs quantum wells prepared by liquid-phase epitaxy. The heterostructures are grown from a Ga solution at T≊650 °C in a slider boat. Chemical lattice images confirm the presence of narrow quantum wells. The well width, however, can vary by one to two atomic layers over distances of order 9–16 nm. Photoluminescence measurements at T=2 K reveal a multiplet of lines for the excitonic [X(e-hh)n=1] transition originating from different columns within each of which the mean well width averaged over the exciton diameter changes by much less than a step height (2.8 Å). The luminescence measurements show that the thickness Lz of the quantum wells varies between 2 and 6 monolayers, with microscopic roughness causing local thickness variations appreciably smaller than one monolayer. Line-shape analysis of the luminescence spectra quantifies the interfacial roughness in terms of a standard deviation σLz=0.2–0.4 monolayer. Time-resolved photoluminescence measurements reveal the same luminescence lifetime of τ≊270 ps at T=4 K for all spectral lines, with direct or indirect excitation of the quantum well. No significant carrier transfer is observed between the different columns. Cathodoluminescence is used to image the micrometer-scale variations in the quantum-well morphology.

  • Received 13 March 1991

DOI:https://doi.org/10.1103/PhysRevB.44.8792

©1991 American Physical Society

Authors & Affiliations

U. Morlock

  • Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 7000 Stuttgart 80, Germany
  • Institut für Festkörperphysik I, Technische Universität Berlin, Hardenbergstrasse 36, 1000 Berlin 12, Germany

J. Christen and D. Bimberg

  • Institut für Festkörperphysik I, Technische Universität Berlin, Hardenbergstrasse 36, 1000 Berlin 12, Germany

E. Bauser and H.-J. Queisser

  • Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 7000 Stuttgart 80, Germany

A. Ourmazd

  • AT&T Bell Laboratories, Holmdel, New Jersey 07733

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Vol. 44, Iss. 16 — 15 October 1991

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