Tuning of long-wavelength emission in InxGa1-xAs quantum dot structures

This work explores the conditions to obtain the extension of the PL emission beyond 1.3 mum in InGaAs quantum dot (QD) structures growth by MOCVD. We found that, by controlling the In incorporation in the barrier embedding the QDs, the wavelength emission can be continuously tuned from 1.25 mum up to 1.4 mum at room temperature. However, the increase in the overall strain of the structures limits the possibility to increase the maximum gain in the QD active device, where an optical density as high as possible is required. By exploring the kinetics of QD surface reconstruction during the GaAs overgrowth, we are able to obtain, for the first time, emission beyond 1.3 pin from InGaAs QDs grown on GaAs matrix. The wavelength is tuned from 1.26 mum up to 1.33 mum and significant improvements in terms of line shape narrowing and room temperature efficiency are obtained. The temperature-dependent quenching of the emission efficiency is reduced down to a factor of 3, the best value ever reported for QD structures emitting at 1.3 mum