Abstract
We report on molecular beam epitaxy growth and properties of rarely studied quaternary In0.4(Al0.75Ga0.25)0.6As self-assembled quantum dots, which show strong and efficient emission of red light from single quantum dots. The increased yield is, among others, due to efficient energy transfer from indirect band-gap Al0.75Ga0.25As barriers. To maximize photon energy emitted from quantum dots, low In composition, xIn = 0.4 was applied, which also lowered the lattice misfit close to the limit of 2D/3D transition in the Stranski–Krastanov growth mode. Time-resolved micro-photoluminescence shows emission at 650–750 nm. Well-resolved single quantum dot photoluminescence lines (decay time of ≈ 1−2 ns) are observed despite a high concentration ≈ 3 × 10 cm−2 of quantum dots. We discuss this observation assuming newly a role of carriers or excitons diffusion/tunneling between quantum dots at high surface concentration of dots and a possible role of lattice disorder inside the dot on the exciton lifetime.
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