InAs quantum dots on the GaAs(2¯5¯1¯1¯)B: STM and photoluminescence studies

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