The authors have developed a multistep molecular-beam epitaxy growth technique which allows them to grow InSb quantum dots with high structural perfection and high density. This technique consists in the deposition at a very low temperature followed by a properly designed annealing step. Fully strained InSb∕GaSb quantum dots with a density exceeding 7×1010cm−2 and lateral sizes in the 20–30nm range have been obtained. Narrow photoluminescence emission is obtained around 3.5μm up to room temperature.
We have investigated the molecular-beam epitaxy ͑MBE͒ of InSb nanostructures on ͑100͒ GaSb substrates. We show that MBE leads to a low density ͑ϳ1−3ϫ 10 9 cm −2 ͒ of large islands even when varying the growth conditions on a wide range ͑substrate temperature ϳ370− 450°C, growth rate ϳ0.3− 1.2 ML/ s͒. Plastic relaxation takes place from the onset of island formation, regardless of the amount of InSb deposited after the two-dimensional to three-dimensional transition. These results show that In adatoms have a very long diffusion length on a Sb-terminated surface and that the energy for dislocation generation in InSb is low. This can be attributed to the low enthalpy of formation and low melting point of InSb. To circumvent this problem we have developed a MBE growth procedure based on the deposition of an amorphous InSb layer at low temperature followed by an annealing step to allow for reorganization to take place. This dramatic change of the growth conditions leads to the formation of small InSb quantum dots with a density in excess of 7 ϫ 10 10 cm −2. Uncapped quantum dots, however, are relaxed. In contrast, buried quantum dots are fully strained and emit near 3.5 m at room temperature. Our results show that although formerly similar the InSb/GaSb materials system behaves completely differently from the InAs/GaAs case study system.
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