Quantum Dots and Quantum Wells Go Head-to-Head
Daniel S. Burgess
In the pursuit of more efficient GaAs-based emitters for telecommunications applications, researchers at Laboratorio Nazionale TASC-INFM and the University of Trieste, both in Italy, have performed a comparison of the photoluminescence of InAsN quantum dots and InGaAsN/GaAs quantum wells produced in the same molecular beam epitaxy reactor. Their work indicates that quantum dots display higher thermal stability than quantum wells, and that the use of GaAsN rather than GaAs barriers with the dots yields more intense and narrower luminescence.
In the experiments, the scientists fabricated 1.3-μm emitters by growing the wells or dots on GaAs substrates by molecular beam epitaxy. Two types of quantum-dot emitters were produced to explore the effect of introduced nitrogen. The completed devices were illuminated with 514.5-nm light from an argon-ion laser, and the resulting photoluminescence was collected for analysis using an amplified germanium photodiode.
The investigators found that postgrowth annealing had no positive effect on the performance of the quantum-dot emitters. In contrast, one hour of postgrowth annealing was necessary to improve the luminescence intensity of the quantum-well devices by a factor of 100, demonstrating the potential manufacturing benefits of employing dots.
A comparison of the temperature dependence of the luminescence from the devices at 10 to 300 K revealed that the intensity of the quantum-dot emitters decreased much less than that of the quantum-well emitters up to 200 K, but then dropped off more strongly. Even at room temperature, however, the intensity from the quantum-dot emitters with GaAsN barriers was comparable to that of the annealed quantum-well devices.
Applied Physics Letters, June 6, 2005, 233107.
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