Direct formation of quantum-sized dots from uniform coherent islands of InGaAs on GaAs surfaces

TLDR

The authors exploit the 2D–3D growth mode transition of highly strained InGaAs on GaAs to form quantum‑sized dots, attributing their remarkable size uniformity to strain‑induced reduction in adatom attachment probabilities. Transmission electron microscopy confirms that interrupting In₀.₅Ga₀.₅As growth at the 2D–3D transition yields dislocation‑free, ~300‑Å diameter dots with 10 % size uniformity and densities from 10⁹ to 10¹¹ cm⁻², which exhibit photoluminescence at ~1.2 eV with intensities comparable to or exceeding those of underlying quantum wells.

Abstract

The 2D–3D growth mode transition during the initial stages of growth of highly strained InGaAs on GaAs is used to obtain quantum-sized dot structures. Transmission electron micrographs reveal that when the growth of In0.5Ga0.5As is interrupted exactly at the onset of this 2D–3D transition, dislocation-free islands (dots) of the InGaAs result. Size distributions indicate that these dots are ∼300 Å in diameter and remarkably uniform to within 10% of this average size. The areal dot densities can be varied between 109 and 1011 cm−2. The uniformity of the dot sizes is explained by a mechanism based on reduction in adatom attachment probabilities due to strain. We unambiguously demonstrate photoluminescence at ∼1.2 eV from these islands by comparing samples with and without dots. The luminescent intensities of the dots are greater than or equal to those of the underlying reference quantum wells.