Role of arsenic vapor pressure in transformation of InAs quantum dots during overgrowth by a GaAs capping layer

The results of a study of the optical properties of self-assembled InAs/GaAs (001) quantum dots (QDs) overgrown under different arsenic pressures, obtained using photoluminescence (PL) and PL excitation spectroscopy, are presented. If the arsenic pressure during overgrowth is low (2.5·10-6 Pa), a series of pronounced QD-related peaks is observed in the 77-K PL spectrum over a 200-meV broad spectral interval with the brightest one located at 1.37 eV. With increasing arsenic pressure, the PL spectrum becomes smoother and is red-shifted to 1.16 eV at 1·10-5 Pa and to 1.26 eV at 3·10-5 Pa. We explain this behavior in terms of enhanced QD decomposition, the mechanism of which is strongly dependent on the arsenic deficiency or excess during the overgrowth process, determined by the arsenic pressure. Supported by the analysis of the wetting layer luminescence, we also conclude that the total indium content in the QD layer decreases with decreasing arsenic pressure during the overgrowth. This study reveals an essential role of the arsenic pressure in the overgrowth of InAs QDs.