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Free keywords:
indium compounds; gallium arsenide; III-V semiconductors; semiconductor quantum dots; scanning tunnelling microscopy; photoluminescence; molecular beam epitaxial growth; low energy electron diffraction; surface reconstruction; scanning-tunneling-microscopy; molecular-beam epitaxy; high-index surfaces; atomic-structure; step structure; GaAs; growth; islands; morphology; shape
Abstract:
The GaAs((2) over bar(5) over bar(1) over bar(1) over bar )B surface was prepared by molecular beam epitaxy and analyzed in situ by scanning tunneling microscopy (STM) and low-energy electron diffraction. Atomically resolved STM images of GaAs((2) over bar(5) over bar(1) over bar(1) over bar )B revealed a 131 reconstruction, terminated by Ga dimers. The deposition of 1.5 ML of InAs onto GaAs((2) over bar(5) over bar(1) over bar(1) over bar )B resulted in the two- to three-dimensional transition with appearance of small InAs quantum dots (QD's) with a very narrow size distribution and a high number density. Low-index (0 (1) over bar(1) over bar), ((1) over bar0 (1) over bar), and ((1) over bar(1) over bar(1) over bar )B facets, a rounded vicinal (00 (1) over bar) region for the main part, and a high-index ((1) over bar(3) over bar(5) over bar )B surface for a flat base determine a shape of the QD's that is totally unsymmetrical. Ex situ-performed photoluminescence measurements revealed a peak of the InAs QD's onGaAs((2) over bar(5) over bar(1) over bar(1) over bar )B with a similar intensity to the peak from the InAs QD's on the reference GaAs(001) surface, but with a higher emission energy and a smaller linewidth, indicating an ensemble of QD's, smaller and more uniform in size. A small redshift (from 1.33 eV to 1.20 eV) of the emission energy was achieved by optimizing the preparation parameters.
