InGaAs quantum dot structures grown in GaAs barrier by metal organic chemical vapor deposition for high efficient long wavelength emission

In this work we present a method to obtain room temperature ground state emission beyond 1.3 ?m from InGaAs QDs, grown by MOCVD, embedded directly into a binary GaAs matrix. The wavelength is tuned from 1.26 ?m up to 1.33 ?m by varying the V/III ratio during the growth of the GaAs cap layer, without using seeding layer or InGaAs wells. A line-shape narrowing (from 36 meV to 24 meV) and a strong reduction of the temperature dependent quenching of the emission (down to a factor 3 from 10K to 300K) are observed, that represent the best value reported for QD structures emitting at 1.3 ?m. The results are explained in term different morphological evolution and surface reconstruction undergone by the InGaAs islands during the GaAs overgrowth that result in larger QD size and in lower In-Ga intermixing. Indeed, cross sectional TEM images show an increase in the QD size of more than 30% with decreasing the AsH3 flow. The overall strain reduction due to the use of the GaAs matrix allows the fabrication of highly efficient staked QD layers. The single and multiple QDs samples show a systematic increase of the emission intensity and similar spectral shape.