Buried Stressor Engineering for Position-Controlled InGaAs Quantum Dots with Local Density Variation for Integrated Quantum Photonics

We report on the monolithic, two-step epitaxial growth of site-controlled InGaAs quantum dots via the buried-stressor method with local quantum dot density variation. As a result of high fabrication accuracy, we achieve low lateral displacements of the individual buried-stressor apertures of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup><mml:mrow><mml:mn>17</mml:mn></mml:mrow> <mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow> <mml:mrow><mml:mn>17</mml:mn></mml:mrow> </mml:mrow> <mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow> <mml:mrow><mml:mn>19</mml:mn></mml:mrow> </mml:mrow> </mml:msubsup> <mml:mi>nm</mml:mi></mml:math> from the mesa centers. We provide extensive microphotoluminescence and cathodoluminescence characterization of the site-controlled quantum dots and give theoretical calculations explaining the effect of the stressor aperture on the quantum dot emission properties, positioning, and density. We show reproducibility of the nucleation process for apertures of the same size and achieve precisely positioned, low- and high-density quantum dot nucleation within one active-layer growth step. The results presented in this work demonstrate the significant potential of the buried-stressor concept in fabricating single photonic chips, simultaneously combining single-photon sources and microlasers featuring different local densities of the site-controlled quantum dots, paving the way for highly functional source modules with applications in photonic quantum technology.