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DOMINO Report Summary

Project ID: 017383
Funded under: FP6-IST
Country: France

Building optical devices at the microscale, nanoscale and beyond

The main objective of the Domino project was very challenging : to investigate the feasibility of antimonides-based quantum-dots (QDs) and nanostructures lasers diodes (LDs) operating at room temperature (RT) in the 3-5 µm wavelength range. During the course of the project we have narrowed our target wavelength to the 3 - 4 µm range, and even more precisely around 3.5 µm where important applications exist (alcane sensing) but no commercial solutions are available. The successful demonstration of Sb-based nanostructures laser diodes could thus pave the way to the development of high performance mid-IR optoelectronic devices and photonic sensors. Since, at the beginning of the project, the properties of Sb-based QDs were unknown. another goal of our project has been to retrieve a clear picture of their basic physical properties. At the same time different nanostructures such as short-period superlattices have also been investigated as active zones of LDs opening the route to further long-term research on semiconductor nanostructures and nano-photonic devices.

The close collaborations between the partners has allowed to achieve many important results in the field of Sb-based nanostructures. The main conclusion drawn from the project in terms of Sb-based QDs is that the InSb/GaSb system is not suitable for light emission for a number of reasons. In contrast, we have demonstrated laser emission at room temperature around 3.5 µm with active zones based on short-period superlattices.

The main results achieved by Domino are summarised below.

InSb-based QDs

- The InSb/GaSb system behaves differently than its InAs/GaAs counterpart. Typical MBE growth conditions lead to a low density of large, plastically relaxed islands.
- A two-step growth procedure, involving the deposition and crystallisation of an amorphous layer, has been developed which allows to form a high density of strained InSb QDs.
- Plastic strain-relaxation of InSb QDs starts at a very early stage (12 nm diameter).
- Strained InSb QDs confined in a GaSb matrix are unstable against cladding overgrowth and/or annealing. InSb tends to dissolve into the matrix.
- Strained InSb/GaSb QDs grown using the two-step procedure emit near 3.5 µm at room temperature, but with a low radiative efficiency.
- Band-structure calculations reveal that light emission from InSb/GaSb QDs most-probably arises from an indirect transition in both the real- and reciprocalspaces.

Short-period superlattices (SPSLs)

- The MBE growth of high-quality InAs/GaSb and InAs/GaSb/InSb SPSLs is well mastered even for layer thickness as low as 1 - 5 MLs, where 1 ML - 0.3 nm.
- Extremely sharp interfaces are achieved.
- The emission of these SPSLs has been tailored from 2.6 to 4 µm at room temperature.
- Spectroscopy as well as band structure calculations indicate that these SPSLs are suitable for light emission in the target wavelength range.


- A robust process, specially dedicated to the GaSb technology, has been developped.
- Scanning Kelvin probe microscopy has been performed on the cleaved edge of laser structures and allowed to draw the potential profile across devices under bias.
- Time resolved spectroscopy indicates that hole escape rather than Auger recombinations seems to dominate the temperature behaviour of GaSb-based nanostructures.
- Laser emission has been achieved with InAs/GaSb SPSLs in the 2.6 - 3.5 µm wavelength range at 90 K and up to 2.8 µm at room temperature.
- Laser emission has been achieved around 3.5 µm at room temperature with InAs/GaSb/InSb SPSLs.
- CW laser operation has been achieved around 3.5 µm up to 220 K with InAs/GaSb/InSb SPSLs.
- Farfield measurements performed with a specially developed set-up indicate single mode operation.

Nanostructure physics

- Lattice-distortion analysis from TEM images and the corresponding simulation softwares have been developed which allow to evaluate interface properties with a very high accuracy.
- This technique has been applied with success to other semiconductor nanostructure including quaternary alloys.
- Cross-section AFM has allowed to investigate buried QDs. The topography image of a cleaved surface of a heterostructure gives rise to protrusions onto the surface indicating the presence of strained nanostructures. The amplitude of these protrusions (and the distribution) is directly related to the strain state (and strain field) of the sample.
- A new software based on the oblate-ellipsoid shape and isotropic elasticity approximation has been developed to calculate the band structure of QDs. It has demonstrated a good predictive value for the band gap in the dot and for the band alignment, and can provide reasonable estimates for the transition energies.
- The model has been applied with success to a large variety of III-V QDs systems.
- A temperature-dependent photoluminescence set-up operating in the mid-IR wavelength range has been developed.%l - A time-resolved spectroscopy set-up operating in the mid-IR wavelength range has been developed. Very few set-up based on the up-conversion technique exist in the world.

Related information

Reported by

Université Montpellier 2
Place Eugène Bataillon
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